WO2022176039A1 - Reception device and reception method - Google Patents

Reception device and reception method Download PDF

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Publication number
WO2022176039A1
WO2022176039A1 PCT/JP2021/005816 JP2021005816W WO2022176039A1 WO 2022176039 A1 WO2022176039 A1 WO 2022176039A1 JP 2021005816 W JP2021005816 W JP 2021005816W WO 2022176039 A1 WO2022176039 A1 WO 2022176039A1
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WO
WIPO (PCT)
Prior art keywords
signal
physical quantity
carrier
optical signal
intensity level
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PCT/JP2021/005816
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French (fr)
Japanese (ja)
Inventor
暁弘 田邉
利明 下羽
陽一 深田
遼 宮武
智暁 吉田
Original Assignee
日本電信電話株式会社
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Application filed by 日本電信電話株式会社 filed Critical 日本電信電話株式会社
Priority to PCT/JP2021/005816 priority Critical patent/WO2022176039A1/en
Priority to PCT/JP2022/000465 priority patent/WO2022176431A1/en
Priority to JP2023500612A priority patent/JPWO2022176431A1/ja
Publication of WO2022176039A1 publication Critical patent/WO2022176039A1/en

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    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • 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
    • H04B10/27—Arrangements for networking
    • H04B10/272—Star-type networks or tree-type networks
    • 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 a receiving device and a receiving method.
  • the transmitter and repeater Video-Optical Line Terminal: V-OLT
  • a branching device may be connected using a coaxial cable, an optical fiber, or the like.
  • a transmitting device may transmit a video signal to a receiving device using an optical signal generated by frequency modulation batch conversion and optical modulation.
  • the optical signal (video signal) transmitted from the transmitting device is relayed to the branching device by the relay device.
  • the branching device distributes the optical signal relayed by the relay device to a plurality of receiving devices.
  • Each receiver generates a carrier signal (video signal) based on the electrical signal by demodulating the electrical signal corresponding to the optical signal input from the branching device.
  • the receiving device outputs the generated carrier wave signal to the video reproducing device.
  • the carrier signal output from the receiver includes a carrier-to-noise ratio (CNR), a composite second order (CSO) amount, and a composite triple beat (CSO) amount.
  • CNR carrier-to-noise ratio
  • CSO composite second order
  • CSO composite triple beat
  • the quality of the carrier signal (original carrier signal) input to the transmitting device must be guaranteed.
  • the intensity level and quality of the optical signal deteriorate according to the transmission distance of the optical signal between the repeater and the receiver.
  • the transmission distance of the optical signal is limited.
  • each threshold for the intensity level of the optical signal input from the repeater to the branching device, the intensity level of the optical signal input to the receiving device from the branching device, and the quality of the carrier signal output from the receiving device the range of transmission distance is determined.
  • the present invention provides a receiver and a receiving method that can improve the possibility of guaranteeing the quality of carrier signals without preparing receivers with different reception performance for different transmission distances. It is intended to
  • a conversion unit that converts a received optical signal into an electrical signal
  • a demodulation unit that generates a carrier signal based on the electrical signal
  • a physical quantity of the electrical signal or a physical quantity of the carrier signal is measured.
  • a controller that adjusts the physical quantity of the received optical signal when the physical quantity of the electrical signal is less than a first threshold or when the physical quantity of the carrier wave signal is less than a second threshold.
  • One aspect of the present invention is a receiving method performed by a receiving device, comprising: a conversion step of converting a received optical signal into an electrical signal; a demodulation step of generating a carrier wave signal based on the electrical signal; a physical quantity measuring step of measuring a physical quantity of a signal or a physical quantity of the carrier signal; and a control step of adjusting the physical quantity of the optical signal.
  • FIG. 1 is a diagram showing a configuration example of an optical transmission system in each embodiment
  • FIG. 2 is a diagram showing a configuration example of a receiving device in the first embodiment
  • FIG. 4 is a flowchart showing an operation example of the optical transmission system in the first embodiment
  • FIG. 11 is a diagram showing a configuration example of a receiving device in the second embodiment
  • FIG. 10 is a flow chart showing an operation example of the optical transmission system in the second embodiment
  • FIG. 12 is a diagram showing a configuration example of a receiving device in the third embodiment
  • FIG. 10 is a flow chart showing an operation example of the optical transmission system in the third embodiment
  • FIG. 4 is a diagram showing a hardware configuration example of a receiving device in each embodiment
  • FIG. 1 is a diagram showing a configuration example of an optical transmission system 1 (video optical transmission network) in each embodiment.
  • the optical transmission system 1 is a system for transmitting optical signals.
  • An optical signal is generated according to, for example, a video signal.
  • the optical transmission system 1 includes a transmitter 2 , a plurality of repeaters 3 , a plurality of branching devices 4 , and a plurality of receivers 5 .
  • a carrier wave signal such as a video signal is input to the transmission device 2 (TA).
  • the transmitter 2 generates an optical signal by batch frequency modulation conversion and optical modulation of the carrier signal. That is, the transmitting device 2 collectively converts the input carrier wave signal (frequency multiplexed signal) (Radio Frequency signal) into a wideband frequency modulation signal (frequency modulation signal).
  • the transmitter 2 modulates the intensity of the optical signal using a wideband frequency modulated signal.
  • the transmitter 2 transmits an optical signal addressed to one or more receivers 5 (V-ONUs) to the repeater 3-0.
  • the repeater 3 is an optical subscriber line terminal (OLT).
  • the repeater 3 is an optical subscriber line terminal (V-OLT) that relays video signals.
  • An optical signal is input from the transmission device 2 to the relay device 3-0.
  • the repeater 3-0 uses an optical fiber to output an optical signal to the repeater 3-n (n is an integer equal to or greater than 1).
  • the optical signal output from the repeater 3-0 is relayed by a plurality of repeaters 3-n.
  • An optical signal is input from the repeater 3-0 to the repeater 3-n.
  • the repeater 3-n relays the optical signal to the branching device 4-n using an optical fiber.
  • the repeater 3-n outputs an optical signal whose intensity level is “P V-OLT ” [dBm] to the branching device 4-n.
  • the repeater 3 may perform dispersion compensation processing on the optical signal as necessary to reduce the influence of the nonlinear optical effect on the optical signal.
  • An optical signal is input from the repeater 3-n to the branching device 4-n.
  • the branching device 4-n distributes the optical signal relayed by the relay device 3-n to a plurality of receiving devices 5-n.
  • the lower limit of the intensity level of the optical signal input to the receiving device 5-n is denoted as "Pdn”.
  • the upper limit of the intensity level of the optical signal input to the receiving device 5-n is expressed as "Pun”.
  • the receiving device 5 is an optical network unit (ONU).
  • the receiving device 5 is an optical network unit (V-ONU) that outputs video signals.
  • An optical signal having a predetermined intensity level [dBm] is input from the branching device 4-n to the receiving device 5-n.
  • an optical signal having an intensity level ranging from "Pd1" to "Pu1” depending on the transmission distance is input from the branching device 4-1 to the receiving device 5-1.
  • an optical signal having an intensity level ranging from "Pd2" to "Pu2” depending on the transmission distance is input from the branching device 4-2 to the receiving device 5-2.
  • the receiving device 5-n generates a carrier wave signal based on the electrical signal by executing demodulation processing on the electrical signal corresponding to the optical signal input from the branching device 4-n.
  • the receiving device 5 outputs the generated carrier signal to a user terminal (not shown).
  • a user terminal is, for example, an information processing device that reproduces video.
  • FIG. 2 is a diagram showing a configuration example of the receiving device 5a in the first embodiment.
  • the receiving device 5a corresponds to the receiving device 5 shown in FIG.
  • the receiver 5a includes a level measuring section 50, a physical quantity measuring section 51a, a control section 52a, a level amplifying section 53a, an optical processing section 54a, a demodulating section 55, and a carrier wave signal amplifying section 56a.
  • the optical processing section 54 a includes a conversion section 540 , a branch section 541 and a preamplifier 542 .
  • the carrier wave signal amplifying section 56 a includes a filter 560 and a post-amplifier 561 .
  • the optical processing section 54a may further include an electric amplifier in at least one of the front stage and the rear stage of the branch section 541. This makes it possible to compensate for the intensity level of the electrical signal even when the intensity level of the electrical signal is lowered due to the branching of the electrical signal by the branching unit 541 .
  • the optical signal is input from the branching device 4 to the level measurement unit 50 .
  • the level measuring section 50 measures the intensity level of the optical signal input from the branching device 4 .
  • the level measuring section 50 outputs a control signal representing the measured intensity level of the optical signal to the control section 52a.
  • the level measuring section 50 outputs the optical signal input from the branching device 4 to the level amplifying section 53a.
  • An electrical signal (frequency-modulated batch-converted signal) is input from the branching section 541 to the physical quantity measuring section 51a.
  • the frequency-modulated batch-converted signal will be referred to as "FM batch-converted signal”.
  • the physical quantity measuring unit 51a measures the strength level of the electrical signal (FM batch conversion signal) input from the branching unit 541 .
  • the physical quantity measurement unit 51a outputs a control signal representing the intensity level of the measured electrical signal (FM batch conversion signal) to the control unit 52a.
  • the control unit 52a acquires from the level measurement unit 50 a control signal representing the intensity level "Pm” of the optical signal.
  • the control unit 52a acquires the control signal representing the intensity level "Em” of the electrical signal (FM batch conversion signal) from the physical quantity measurement unit 51a.
  • the control unit 52a receives data representing the range “Pd to Pu” [dBm] of the intensity level of the optical signal that can be received by the conversion unit 540, and the intensity level of the electrical signal required for the demodulation processing executed by the demodulation unit 55.
  • Data representing "E" is stored in advance.
  • the control unit 52a controls the intensity level “Em” of the electric signal to be equal to or higher than the intensity level “E” and the intensity level of the optical signal input to the conversion unit 540 to be within the range from the lower limit “Pd” to the upper limit “Pu”.
  • the amplification gain of the optical signal in the level amplifier 53a is adjusted so as to be contained.
  • the control section 52a outputs a control signal representing the amplification gain to the level amplification section 53a.
  • the control unit 52a determines whether the intensity level "Em” of the electric signal is lower than the intensity level "E” of the electric signal. When the intensity level “Em” of the electric signal is lower than the intensity level "E” of the electric signal, the control unit 52a outputs an optical signal having an intensity level higher than the intensity level "Pm” of the optical signal by a certain width "Pw". The amplification gain of the optical signal in the level amplification section 53 a is adjusted so that the level amplification section 53 a outputs to the conversion section 540 .
  • the control unit 52a determines again whether the intensity level "Em” of the electric signal is lower than the intensity level "E” of the electric signal.
  • the control unit 52a readjusts the amplification gain of the optical signal in the level amplifying unit 53a.
  • the controller 52a readjusts the amplification gain of the optical signal in the level amplifier 53a until it is determined that the intensity level "Em” of the electrical signal is equal to or higher than the intensity level "E” of the electrical signal.
  • the controller 52a stops the amplification gain readjustment process so that the intensity level of the optical signal does not exceed the upper limit "Pu".
  • the control algorithm executed by the control unit 52a is not limited to a specific algorithm.
  • the control unit 52a executes amplification gain adjustment processing using, for example, an optimization method such as a binary search method or a nonlinear least-squares method.
  • an optimization method such as a binary search method or a nonlinear least-squares method.
  • the electrical signal strength level "Em" may not be optimized if the quality of the carrier signal (e.g. carrier-to-noise ratio) reaches a quality criterion (threshold) for video reproduction. .
  • An optical signal corresponding to the carrier wave signal is input from the level measuring section 50 to the level amplifying section 53a (variable amplifying section).
  • the level amplifier 53a acquires a control signal representing an amplification gain from the controller 52a.
  • the level amplifier 53a amplifies the intensity level of the optical signal based on the amplification gain instructed using the control signal.
  • the level amplifier 53 a outputs the optical signal to the converter 540 .
  • the optical processing unit 54a is, for example, a receiver optical sub-assembly (ROSA).
  • the conversion unit 540 photoelectric conversion unit
  • An optical signal is input to the converter 540 from the level amplifier 53a.
  • the converter 540 converts the optical signal into an electrical signal (FM batch conversion signal).
  • Conversion unit 540 outputs the converted electrical signal to branch unit 541 .
  • the branching unit 541 acquires the electrical signal from the conversion unit 540.
  • the branching unit 541 distributes the electric signal (FM batch conversion signal) to the preamplifier 542 and the physical quantity measuring unit 51a.
  • the preamplifier 542 is, for example, a trans-impedance amplifier (TIA).
  • the preamplifier 542 acquires the electrical signal (FM batch conversion signal) from the branch section 541 .
  • Preamplifier 542 amplifies the intensity level of the electrical signal based on a predetermined amplification gain.
  • the preamplifier 542 outputs to the demodulator 55 an electrical signal with an intensity level of “E” or higher.
  • the demodulator 55 acquires from the preamplifier 542 an electrical signal (FM batch-converted signal) whose intensity level is "E" or higher.
  • the demodulator 55 generates a carrier wave signal (video signal) based on the electrical signal by performing demodulation processing on the electrical signal (FM batch conversion signal).
  • Demodulator 55 outputs the carrier signal to filter 560 .
  • the carrier wave signal amplifier 56a amplifies the strength level of the carrier wave signal.
  • Filter 560 acquires the carrier wave signal (video signal) from demodulator 55 .
  • Filter 560 is a low-pass filter (LPF).
  • the filter 560 passes the low frequency carrier wave signal (video signal). That is, the filter 560 removes noise from the carrier signal (video signal).
  • the post-amplifier 561 amplifies the intensity level of the noise-removed carrier wave signal (video signal) based on a predetermined amplification gain.
  • the post-amplifier 561 outputs a carrier wave signal (video signal) whose intensity level is amplified to a user terminal (not shown).
  • the quality of the carrier signal whose intensity level is amplified is above the predetermined threshold. That is, the carrier signal has a guaranteed carrier-to-noise ratio, an amount of complex second-order distortion, and an amount of complex third-order distortion.
  • FIG. 3 is a flow chart showing an operation example of the optical transmission system 1 in the first embodiment.
  • the optical transmission system 1 performs the operation shown using the flowchart in FIG. 3 at predetermined intervals.
  • the level measurement unit 50 measures the intensity level of the input optical signal.
  • the level amplifier 53a amplifies the intensity level of the optical signal based on the amplification gain instructed by the controller 52a using the control signal (step S101).
  • the converter 540 converts the optical signal into an electrical signal (FM batch conversion signal).
  • the branching unit 541 distributes the electric signal (FM batch conversion signal) to the preamplifier 542 and the physical quantity measuring unit 51a.
  • the physical quantity measuring unit 51a measures the intensity level of the electrical signal (FM batch conversion signal) input from the branching unit 541 (step S102).
  • the physical quantity measuring unit 51a measures the intensity level of the electrical signal (FM batch conversion signal) input from the branching unit 541 (step S103).
  • the control unit 52a determines whether or not the electric signal strength level "Em” is equal to or higher than the electric signal strength level "E" (threshold value or higher) (step S104). When it is determined that the electric signal intensity level "Em” is equal to or higher than the electric signal intensity level "E” (step S104: YES), the optical transmission system 1 performs the operation shown using the flowchart in FIG. finish.
  • control unit 52a causes the level amplifying unit 53a to increase the optical signal intensity level by a certain width.
  • a control signal is generated to further amplify by "Pw”.
  • the level amplifier 53a further amplifies the intensity level of the optical signal by a certain width "Pw" (step S105).
  • the control unit 52a determines whether or not the intensity level further amplified by the constant width "Pw" exceeds the upper limit "Pu” (step S106). If it is determined that the intensity level further amplified by the constant width "Pw” is equal to or lower than the upper limit "Pu” (step S106: NO), the optical transmission system 1 performs the operation shown using the flowchart in FIG. finish. If it is determined that the intensity level further amplified by the constant width "Pw” exceeds the upper limit "Pu” (step S106: YES), the control unit 52a causes the level amplifier 53a to increase the intensity level of the optical signal by the constant width. A control signal is generated to stop the process of further amplification. The level amplifier 53a amplifies the intensity level of the optical signal with the upper limit amplification gain (step S107).
  • the conversion unit 540 converts the received optical signal (FM batch conversion signal) into an electrical signal.
  • a demodulator 55 generates a carrier wave signal based on the electrical signal.
  • the physical quantity measuring section 51 a measures the physical quantity of the electrical signal output from the converting section 540 .
  • the controller 52a adjusts the physical quantity of the received optical signal when the physical quantity (intensity level "Em") of the electrical signal is less than the first threshold (intensity level "E").
  • the physical quantity of the electrical signal is the intensity level of the electrical signal.
  • the controller 52a amplifies the intensity level of the received optical signal when the physical quantity of the electrical signal is less than the first threshold.
  • the receiving device 5a improves the quality of the output carrier signal by adjusting the intensity level of the input optical signal. As a result, the transmission distance between the relay device 3-n and the receiving device 5a can be increased, so that the receiving device 5a with the same reception performance can be used in a wider area.
  • Degradation of the carrier-to-noise ratio (CNR) is affected by both noise in the optical signal transmission path and noise inside the receiver 5a (V-ONU).
  • the intensity level of the optical signal input to the receiver 5a is low, the influence of noise inside the receiver 5a is greater than the influence of noise in the transmission line of the optical signal. Therefore, by amplifying the intensity level of the optical signal input to the receiving device 5a, the influence of noise inside the receiving device 5a is alleviated, so deterioration of the carrier-to-noise ratio (CNR) can be suppressed. It is possible.
  • the second embodiment differs from the first embodiment in that the quality of the carrier wave signal (video signal) output from the postamplifier is measured.
  • 2nd Embodiment demonstrates centering around the difference with 1st Embodiment.
  • FIG. 4 is a diagram showing a configuration example of the receiving device 5b in the second embodiment.
  • the receiving device 5b corresponds to the receiving device 5 shown in FIG.
  • the receiver 5b includes a level measuring section 50, a physical quantity measuring section 51b, a control section 52b, a level amplifying section 53b, an optical processing section 54b, a demodulating section 55, and a carrier wave signal amplifying section 56b.
  • the control section 52b, the level amplification section 53b, and the optical processing section 54b correspond to the control section 52a, the level amplification section 53a, and the optical processing section 54a shown in FIG.
  • the optical processing section 54 b includes a conversion section 540 and a preamplifier 542 .
  • the carrier wave signal amplifying section 56b includes a filter 560, a post-amplifier 561, and a branching section 562.
  • the carrier wave signal amplification section 56b may further include an electric amplifier in at least one of the front stage and the rear stage of the branch section 562.
  • An electric signal (video signal) is input from the branching unit 562 to the physical quantity measuring unit 51b.
  • the physical quantity measuring unit 51b measures the carrier-to-noise ratio (CNR) of the electrical signal (video signal) input from the branching unit 562.
  • CNR carrier-to-noise ratio
  • the physical quantity measurement unit 51 b may measure the amount of complex second-order distortion and the amount of complex third-order distortion of the electrical signal input from the branching unit 562 .
  • the physical quantity measuring unit 51b outputs a control signal representing the measured carrier-to-noise ratio “CNRm(i)” of the electrical signal (video signal) to the control unit 52b.
  • the code 'i' is an integer greater than 0 and less than the integer 'N', where the integer 'N' represents the total number of video channels.
  • the control unit 52b acquires from the level measurement unit 50 a control signal representing the intensity level "Pm" of the optical signal.
  • the control unit 52b acquires a control signal representing the carrier-to-noise ratio of the electric signal (video signal) from the physical quantity measurement unit 51b.
  • the control unit 52b provides data representing the range of intensity levels of optical signals that the conversion unit 540 can receive, “Pd to Pu” [dBm], and the carrier-to-noise ratio “CNR(i )” is stored in advance.
  • the control unit 52b controls the intensity level “Em” of the electric signal to be equal to or higher than the intensity level “E” and the intensity level of the optical signal input to the conversion unit 540 to be within the range from the lower limit “Pd” to the upper limit “Pu”.
  • the amplification gain of the optical signal in the level amplification unit 53b is adjusted so as to be contained.
  • the control section 52b outputs a control signal representing the amplification gain to the level amplification section 53b.
  • the control unit 52b determines whether or not the carrier-to-noise ratio "CNRm(i)" of the electrical signal (video signal) is lower than the carrier-to-noise ratio "CNR(i)” of the electrical signal (video signal).
  • the control unit 52b controls the control unit 52b to set the power level “Pm” of the optical signal to a certain width “
  • the amplification gain of the optical signal in the level amplification section 53b is adjusted so that the level amplification section 53b outputs an optical signal having an intensity level higher by "Pw” to the conversion section 540.
  • the control unit 52b determines again whether the carrier-to-noise ratio "CNRm(i)" of the electrical signal is lower than the carrier-to-noise ratio "CNR(i)" of the electrical signal (video signal).
  • the control unit 52b amplifies the optical signal in the level amplifier 53b. Readjust the gain.
  • the controller 52b amplifies the optical signal in the level amplifier 53b until it is determined that the carrier-to-noise ratio "CNRm(i)" of the electrical signal is greater than or equal to the carrier-to-noise ratio "CNR(i)” of the electrical signal. Readjust the gain. However, if the intensity level of the optical signal exceeds the upper limit "Pu", the controller 52b stops the amplification gain readjustment process so that the intensity level of the optical signal does not exceed the upper limit "Pu". Further, when the intensity level of the optical signal falls below the lower limit "Pd", the controller 52b stops the amplification gain readjustment process so that the intensity level of the optical signal does not fall below the lower limit "Pd".
  • the control algorithm executed by the control unit 52b is not limited to a specific algorithm.
  • the control unit 52b executes amplification gain adjustment processing using an optimization method such as a binary search method or a nonlinear least-squares method. Note that if the quality of the carrier signal (e.g., carrier-to-noise ratio) reaches a quality standard (threshold) that allows video reproduction, the carrier-to-noise ratio "CNRm(i)" of the electrical signal is optimized. It doesn't have to be.
  • An optical signal corresponding to the carrier signal is input from the level measuring section 50 to the level amplifying section 53b (variable amplifying section).
  • the level amplifier 53b acquires the control signal representing the amplification gain from the controller 52b.
  • the level amplifier 53b amplifies the intensity level of the optical signal based on the amplification gain instructed using the control signal.
  • the level amplifier 53 b outputs the optical signal to the converter 540 .
  • the optical processor 54b is, for example, a receiver optical subassembly.
  • An optical signal is input to the converter 540 from the level amplifier 53b.
  • the converter 540 converts the optical signal into an electrical signal (FM batch conversion signal).
  • Conversion unit 540 outputs the converted electrical signal to preamplifier 542 .
  • the post-amplifier 561 outputs the carrier wave signal (video signal) whose intensity level is amplified to the branching unit 562 .
  • the branching unit 562 acquires the carrier wave signal (video signal) from the post-amplifier 561 .
  • the branching unit 562 distributes the carrier wave signal (video signal) to the user terminal (not shown) and the physical quantity measuring unit 51b.
  • FIG. 5 is a flow chart showing an operation example of the optical transmission system 1 in the second embodiment.
  • the optical transmission system 1 performs the operation shown using the flowchart in FIG. 5 at predetermined intervals.
  • the operations from step S201 to step S202 are the same as the operations from step S101 to step S102 shown in FIG.
  • the demodulator 55 generates a carrier wave signal (video signal) based on the electrical signal by performing demodulation processing on the electrical signal (FM batch conversion signal) (step S203).
  • the physical quantity measuring unit 51b measures at least one of the carrier-to-noise ratio (CNR) of the electrical signal input from the branching unit 562, the amount of complex second-order distortion of the carrier signal, and the amount of complex third-order distortion of the carrier signal. One is measured (step S204).
  • CNR carrier-to-noise ratio
  • control unit 52b determines whether the carrier-to-noise ratio is equal to or higher than the threshold value of the carrier signal (equal to or higher than the quality standard) (step S205). If it is determined that the carrier-to-noise ratio is greater than or equal to the threshold value of the carrier signal (ie, greater than or equal to the quality standard) (step S205: YES), the optical transmission system 1 terminates the operation shown using the flowchart in FIG.
  • step S205 If it is determined that the carrier-to-noise ratio is less than the carrier signal threshold (less than the quality standard) (step S205: NO), the control unit 52b proceeds to step S206.
  • the operations from step S206 to step S208 are the same as the operations from step S105 to step S107 shown in FIG.
  • the conversion unit 540 converts the received optical signal into an electrical signal.
  • a demodulator 55 generates a carrier wave signal based on the electrical signal.
  • the physical quantity measuring section 51b measures the physical quantity of the carrier wave signal output from the post-amplifier 561.
  • the physical quantity of the carrier signal is, for example, at least one of the carrier-to-noise ratio, the amount of composite second-order distortion, and the amount of composite third-order distortion.
  • the controller 52b adjusts the physical quantity of the received optical signal when the physical quantity of the carrier signal is less than the second threshold (less than the quality standard). For example, the controller 52b amplifies the intensity level of the received optical signal when the physical quantity of the carrier signal is less than the second threshold.
  • FIG. 6 is a diagram showing a configuration example of the receiving device 5c in the third embodiment.
  • the receiving device 5c corresponds to the receiving device 5 shown in FIG.
  • the receiving device 5c includes a physical quantity measuring section 51c, a control section 52c, a level amplifying section 53c, an optical processing section 54c, a demodulating section 55, a carrier wave signal amplifying section 56b, and a compensating section 57.
  • the control unit 52c, the level amplification unit 53c, and the optical processing unit 54c correspond to the control unit 52b, the level amplification unit 53b, and the optical processing unit 54b shown in FIG.
  • the optical processing section 54 c includes a conversion section 540 and a preamplifier 542 .
  • the carrier wave signal amplifying section 56 c includes a filter 560 , a post-amplifier 561 and a branching section 562 .
  • the carrier wave signal amplification section 56c may further include an electric amplifier in at least one of the front stage and the rear stage of the branch section 562.
  • An optical signal is input from the branching device 4 to the compensation unit 57 .
  • the compensation unit 57 acquires a control signal representing the amount of compensation from the control unit 52c.
  • the compensator 57 compensates for waveform distortion of the optical signal due to chromatic dispersion based on the amount of compensation instructed by the controller 52c using the control signal.
  • the compensator 57 outputs the optical signal whose waveform distortion has been compensated for to the level amplifier 53c.
  • the control unit 52c controls data representing the range “Pd to Pu” [dBm] of the intensity level of the optical signal that can be received by the conversion unit 540, and the carrier-to-noise ratio “CNR(i )” is stored in advance.
  • the control unit 52c controls the intensity level “Em” of the electric signal to be equal to or higher than the intensity level “E” and the intensity level of the optical signal input to the conversion unit 540 to be within the range from the lower limit “Pd” to the upper limit “Pu”.
  • the amplification gain of the optical signal in the level amplification unit 53c is adjusted so as to be contained.
  • the controller 52c outputs a control signal representing the amplification gain to the level amplifier 53c.
  • the control unit 52c determines whether the carrier-to-noise ratio "CNRm(i)" of the electrical signal is smaller than the carrier-to-noise ratio "CNR(i)" of the electrical signal (video signal). When the carrier-to-noise ratio "CNRm(i)” of the electrical signal is smaller than the carrier-to-noise ratio "CNR(i)” of the electrical signal, the control unit 52c increases the current compensation amount by a certain width "Vw". The amount of compensation for the waveform distortion of the optical signal in the compensator 57 is adjusted so that the compensator 57 compensates for the waveform of the optical signal with the amount of compensation.
  • the control unit 52c determines again whether the carrier-to-noise ratio "CNRm(i)" of the electrical signal (video signal) is smaller than the carrier-to-noise ratio "CNR(i)” of the electrical signal (video signal).
  • the controller 52c controls the waveform distortion of the optical signal in the compensator 57. Readjust the amount of compensation for The controller 52c may readjust the amplification gain of the optical signal in the level amplifier 53c.
  • the controller 52c controls the waveform distortion of the optical signal in the compensator 57 until it is determined that the carrier-to-noise ratio "CNRm(i)" of the electrical signal is greater than or equal to the carrier-to-noise ratio "CNR(i)” of the electrical signal. Readjust the amount of compensation for The controller 52c may readjust the amplification gain of the optical signal in the level amplifier 53c. However, if the waveform distortion compensation amount exceeds the upper limit of the compensation amount, the control unit 52c stops the compensation amount readjustment process so that the waveform distortion compensation amount does not exceed the upper limit of the compensation amount.
  • the control algorithm executed by the control unit 52c is not limited to a specific algorithm.
  • the control unit 52b executes compensation amount adjustment processing using, for example, an optimization method such as a binary search method or a nonlinear least-squares method.
  • FIG. 7 is a flow chart showing an operation example of the optical transmission system 1 in the third embodiment.
  • the optical transmission system 1 performs the operation shown using the flowchart in FIG. 7 at predetermined intervals.
  • the compensation unit 57 compensates for waveform distortion of the optical signal due to chromatic dispersion based on the amount of compensation instructed by the control unit 52c using the control signal (step S301).
  • the operations from step S302 to step S305 are the same as the operations from step S202 to step S205 shown in FIG.
  • step S305: NO the controller 52c causes the compensator 57 to set the amount of compensation for the waveform distortion of the optical signal to the constant width "Vw ” to further increase the control signal.
  • the compensation unit 57 further increases the amount of compensation for the waveform distortion of the optical signal by the constant width "Vw” (step S306).
  • the control unit 52c determines whether or not the compensation amount further increased by the constant width "Vw" exceeds the upper limit (step S307). If it is determined that the amount of compensation further increased by the constant width "Vw” is equal to or less than the upper limit (step S307: NO), the optical transmission system 1 terminates the operation shown using the flowchart in FIG. If it is determined that the compensation amount further increased by the constant width "Vw" exceeds the upper limit (step S307: YES), the control unit 52c causes the compensation unit 57 to further increase the compensation amount for the waveform distortion of the optical signal by the constant width. A control signal is generated to stop the increasing process. The compensation unit 57 compensates for the waveform distortion of the optical signal with the upper limit compensation amount (step S308).
  • the compensator 57 compensates for waveform distortion of the received optical signal.
  • the converter 540 converts the received optical signal into an electrical signal.
  • a demodulator 55 generates a carrier wave signal based on the electrical signal.
  • the physical quantity measuring unit 51c measures the physical quantity of the carrier signal. For example, at least one of the carrier-to-noise ratio, the amount of composite second order distortion, and the amount of composite third order distortion.
  • the controller 52c adjusts the physical quantity of the received optical signal when the physical quantity of the carrier signal is less than the second threshold (less than the quality standard). For example, when the physical quantity of the carrier signal is less than the second threshold, the controller 52c increases the amount of compensation for waveform distortion of the received optical signal.
  • the receiving device 5c improves the quality of the output carrier signal by compensating for the waveform distortion of the input optical signal.
  • the transmission distance between the relay device 3-n and the receiving device 5c can be lengthened, so that the receiving device 5c with the same reception performance can be used in a wider area.
  • the transmitter 2 base station side
  • the access between the receiver 5 port of the optical amplifier for access
  • the user terminal not shown
  • the quality of the carrier wave signal can be improved even when the access distance between the receiving device 5 and the user terminal (not shown) varies. is possible.
  • FIG. 8 is a diagram showing a hardware configuration example of the receiving device 5 in each embodiment.
  • a processor 100 such as a CPU (Central Processing Unit) and a storage device 102 having a non-volatile recording medium (non-temporary recording medium) and a memory 101. It is implemented as software by executing a program stored in the .
  • the program may be recorded on a computer-readable recording medium.
  • Computer-readable recording media include portable media such as flexible discs, magneto-optical discs, ROM (Read Only Memory), CD-ROM (Compact Disc Read Only Memory), and storage such as hard disks built into computer systems. It is a non-temporary recording medium such as a device.
  • Some or all of the functional units of the receiving device 5 are, for example, LSI (Large Scale Integrated circuit), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), FPGA (Field Programmable Gate Array), etc. It may be implemented using hardware including electronic circuits or circuitry.
  • the present invention is applicable to optical transmission systems that transmit video signals and the like using optical signals.

Abstract

This reception device comprises: a conversion unit that converts a received optical signal into an electrical signal; a demodulation unit that generates a carrier signal on the basis of the electrical signal; a physical quantity measurement unit that measures the physical quantity of the electrical signal or the physical quantity of the carrier signal; and a control unit that adjusts the physical quantity of the received optical signal when the physical quantity of the electrical signal is less than a first threshold value, or the physical quantity of the carrier signal is less than a second threshold value. The physical quantity of the electrical signal is the intensity level of the received optical signal. The control unit amplifies the intensity level of the received optical signal when the physical quantity of the electrical signal is less than the first threshold value. The physical quantity of the carrier signal is at least one of the carrier-to-noise ratio, the amount of composite second-order distortion, or the amount of composite third-order distortion. The control unit amplifies the intensity level of the received optical signal when the physical quantity of the carrier signal is less than the second threshold value.

Description

受信装置及び受信方法Receiving device and receiving method
　本発明は、受信装置及び受信方法に関する。 The present invention relates to a receiving device and a receiving method.
　光伝送システムでは、最も上り側の送信装置（Transmission Amplifier : TA）から、最も下り側の受信装置(Video-Optical Network Unit : V-ONU)に向けて、送信装置と中継装置(Video-Optical Line Terminal : V-OLT)と分岐装置と受信装置とが、同軸ケーブル及び光ファイバ等を用いて接続されている場合がある。 In an optical transmission system, the transmitter and repeater (Video-Optical Line Terminal: V-OLT), a branching device, and a receiving device may be connected using a coaxial cable, an optical fiber, or the like.
　光伝送システムでは、周波数変調（Frequency Modulation）一括変換と光変調とによって生成された光信号を用いて、送信装置が受信装置に映像信号を送信する場合がある。ここで、送信装置から送信された光信号（映像信号）は、中継装置によって、分岐装置に中継される。分岐装置は、中継装置によって中継された光信号を、複数の受信装置に分配する。各受信装置は、分岐装置から入力された光信号に応じた電気信号に対して復調処理を実行することによって、搬送波信号（映像信号）を電気信号に基づいて生成する。受信装置は、生成された搬送波信号を、映像再生装置に出力する。 In an optical transmission system, a transmitting device may transmit a video signal to a receiving device using an optical signal generated by frequency modulation batch conversion and optical modulation. Here, the optical signal (video signal) transmitted from the transmitting device is relayed to the branching device by the relay device. The branching device distributes the optical signal relayed by the relay device to a plurality of receiving devices. Each receiver generates a carrier signal (video signal) based on the electrical signal by demodulating the electrical signal corresponding to the optical signal input from the branching device. The receiving device outputs the generated carrier wave signal to the video reproducing device.
　受信装置から出力された搬送波信号には、搬送波対雑音比（Carrier-to-Noise ratio : CNR）と、複合２次歪（Composite Second Order : CSO）の量と、複合３次歪（Composite Triple Beat : CTB）の量との各閾値が、搬送波信号の種別ごとに定められている。これによって、映像再生のための品質が保証される。光伝送システムでは、受信装置から出力される搬送波信号の品質が、これらの各閾値に基づいて保証されている必要がある（非特許文献１参照）。 The carrier signal output from the receiver includes a carrier-to-noise ratio (CNR), a composite second order (CSO) amount, and a composite triple beat (CSO) amount. : CTB) amount and each threshold are defined for each type of carrier signal. This ensures quality for video playback. In optical transmission systems, the quality of carrier signals output from receivers must be guaranteed based on these thresholds (see Non-Patent Document 1).
　受信装置から出力される搬送波信号の品質が保証されるためには、送信装置に入力された搬送波信号（元の搬送波信号）の品質が保証されている必要がある。しかしながら、送信装置に入力された搬送波信号の品質が保証されたとしても、中継装置と受信装置との間における光信号の伝送距離に応じて、光信号の強度レベル及び品質は劣化する。 In order to guarantee the quality of the carrier signal output from the receiving device, the quality of the carrier signal (original carrier signal) input to the transmitting device must be guaranteed. However, even if the quality of the carrier wave signal input to the transmitter is guaranteed, the intensity level and quality of the optical signal deteriorate according to the transmission distance of the optical signal between the repeater and the receiver.
　このため、送信装置に入力された搬送波信号の品質が一定である場合には、光信号の伝送距離が制限される。換言すれば、分岐装置に中継装置から入力される光信号の強度レベルと、受信装置に分岐装置から入力される光信号の強度レベルと、受信装置から出力される搬送波信号の品質とに対する各閾値に応じて、伝送距離の範囲が定まる。このように、光信号の伝送距離が異なる場合には、伝送距離ごとに異なる受信性能の受信装置が用意されなければ、搬送波信号の品質を保証することができない場合がある。 Therefore, if the quality of the carrier signal input to the transmitter is constant, the transmission distance of the optical signal is limited. In other words, each threshold for the intensity level of the optical signal input from the repeater to the branching device, the intensity level of the optical signal input to the receiving device from the branching device, and the quality of the carrier signal output from the receiving device , the range of transmission distance is determined. As described above, when optical signals are transmitted over different transmission distances, the quality of carrier signals cannot be guaranteed unless receivers having different reception performance are prepared for each transmission distance.
　上記事情に鑑み、本発明は、伝送距離ごとに異なる受信性能の受信装置が用意されなくても、搬送波信号の品質を保証する可能性を向上させることが可能である受信装置及び受信方法を提供することを目的としている。 In view of the above circumstances, the present invention provides a receiver and a receiving method that can improve the possibility of guaranteeing the quality of carrier signals without preparing receivers with different reception performance for different transmission distances. It is intended to
　本発明の一態様は、受信された光信号を電気信号に変換する変換部と、前記電気信号に基づいて搬送波信号を生成する復調部と、前記電気信号の物理量又は前記搬送波信号の物理量を測定する物理量測定部と、前記電気信号の物理量が第１閾値未満である場合、又は、前記搬送波信号の物理量が第２閾値未満である場合、前記受信された光信号の物理量を調整する制御部とを備える受信装置である。 According to one aspect of the present invention, a conversion unit that converts a received optical signal into an electrical signal, a demodulation unit that generates a carrier signal based on the electrical signal, and a physical quantity of the electrical signal or a physical quantity of the carrier signal is measured. and a controller that adjusts the physical quantity of the received optical signal when the physical quantity of the electrical signal is less than a first threshold or when the physical quantity of the carrier wave signal is less than a second threshold. is a receiving device comprising
　本発明の一態様は、受信装置が実行する受信方法であって、受信された光信号を電気信号に変換する変換ステップと、前記電気信号に基づいて搬送波信号を生成する復調ステップと、前記電気信号の物理量又は前記搬送波信号の物理量を測定する物理量測定ステップと、前記電気信号の物理量が第１閾値未満である場合、又は、前記搬送波信号の物理量が第２閾値未満である場合、前記受信された光信号の物理量を調整する制御ステップとを含む受信方法である。 One aspect of the present invention is a receiving method performed by a receiving device, comprising: a conversion step of converting a received optical signal into an electrical signal; a demodulation step of generating a carrier wave signal based on the electrical signal; a physical quantity measuring step of measuring a physical quantity of a signal or a physical quantity of the carrier signal; and a control step of adjusting the physical quantity of the optical signal.
　本発明により、伝送距離ごとに異なる受信性能の受信装置が用意されなくても、搬送波信号の品質を向上させることが可能である。 According to the present invention, it is possible to improve the quality of carrier wave signals without preparing receivers with different reception performance for each transmission distance.
各実施形態における、光伝送システムの構成例を示す図である。1 is a diagram showing a configuration example of an optical transmission system in each embodiment; FIG. 第１実施形態における、受信装置の構成例を示す図である。2 is a diagram showing a configuration example of a receiving device in the first embodiment; FIG. 第１実施形態における、光伝送システムの動作例を示すフローチャートである。4 is a flowchart showing an operation example of the optical transmission system in the first embodiment; 第２実施形態における、受信装置の構成例を示す図である。FIG. 11 is a diagram showing a configuration example of a receiving device in the second embodiment; FIG. 第２実施形態における、光伝送システムの動作例を示すフローチャートである。10 is a flow chart showing an operation example of the optical transmission system in the second embodiment; 第３実施形態における、受信装置の構成例を示す図である。FIG. 12 is a diagram showing a configuration example of a receiving device in the third embodiment; FIG. 第３実施形態における、光伝送システムの動作例を示すフローチャートである。10 is a flow chart showing an operation example of the optical transmission system in the third embodiment; 各実施形態における、受信装置のハードウェア構成例を示す図であFIG. 4 is a diagram showing a hardware configuration example of a receiving device in each embodiment;
　本発明の実施形態について、図面を参照して詳細に説明する。
　（第１実施形態）
　図１は、各実施形態における、光伝送システム１（映像光伝送ネットワーク）の構成例を示す図である。光伝送システム１は、光信号を伝送するシステムである。光信号は、例えば映像信号に応じて生成される。光伝送システム１は、送信装置２と、複数の中継装置３と、複数の分岐装置４と、複数の受信装置５とを備える。 Embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration example of an optical transmission system 1 (video optical transmission network) in each embodiment. The optical transmission system 1 is a system for transmitting optical signals. An optical signal is generated according to, for example, a video signal. The optical transmission system 1 includes a transmitter 2 , a plurality of repeaters 3 , a plurality of branching devices 4 , and a plurality of receivers 5 .
　送信装置２（TA）には、映像信号等の搬送波信号が入力される。送信装置２は、搬送波信号に対する周波数変調一括変換と光変調とによって、光信号を生成する。すなわち、送信装置２は、入力された搬送波信号（周波数多重信号）（Radio Frequency signal）を、広帯域な周波数変調信号（frequency modulation signal）に一括変換する。送信装置２は、広帯域な周波数変調信号を用いて、光信号の強度を変調する。送信装置２は、１台以上の受信装置５（V-ONU）宛ての光信号を、中継装置３－０に送信する。 A carrier wave signal such as a video signal is input to the transmission device 2 (TA). The transmitter 2 generates an optical signal by batch frequency modulation conversion and optical modulation of the carrier signal. That is, the transmitting device 2 collectively converts the input carrier wave signal (frequency multiplexed signal) (Radio Frequency signal) into a wideband frequency modulation signal (frequency modulation signal). The transmitter 2 modulates the intensity of the optical signal using a wideband frequency modulated signal. The transmitter 2 transmits an optical signal addressed to one or more receivers 5 (V-ONUs) to the repeater 3-0.
　中継装置３は、光加入者線端局装置（OLT）である。以下では、中継装置３は、映像信号を中継する光加入者線端局装置（V-OLT）である。中継装置３－０には、光信号が送信装置２から入力される。中継装置３－０は、光ファイバを利用して、光信号を中継装置３－ｎ（ｎは、１以上の整数）に出力する。中継装置３－０から出力された光信号は、複数の中継装置３－ｎによって中継される。 The repeater 3 is an optical subscriber line terminal (OLT). In the following description, the repeater 3 is an optical subscriber line terminal (V-OLT) that relays video signals. An optical signal is input from the transmission device 2 to the relay device 3-0. The repeater 3-0 uses an optical fiber to output an optical signal to the repeater 3-n (n is an integer equal to or greater than 1). The optical signal output from the repeater 3-0 is relayed by a plurality of repeaters 3-n.
　中継装置３－ｎには、光信号が中継装置３－０から入力される。中継装置３－ｎは、光ファイバを利用して、光信号を分岐装置４－ｎに中継する。中継装置３－ｎは、強度レベルが「ＰＶ－ＯＬＴ」［ｄＢｍ］である光信号を、分岐装置４－ｎに出力する。なお、中継装置３は、光信号における非線形光学効果の影響を低減するための分散補償処理を、必要に応じて光信号に対して実行してもよい。 An optical signal is input from the repeater 3-0 to the repeater 3-n. The repeater 3-n relays the optical signal to the branching device 4-n using an optical fiber. The repeater 3-n outputs an optical signal whose intensity level is “P V-OLT ” [dBm] to the branching device 4-n. Note that the repeater 3 may perform dispersion compensation processing on the optical signal as necessary to reduce the influence of the nonlinear optical effect on the optical signal.
　分岐装置４－ｎには、光信号が中継装置３－ｎから入力される。分岐装置４－ｎは、中継装置３－ｎによって中継された光信号を、複数の受信装置５－ｎに分配する。 An optical signal is input from the repeater 3-n to the branching device 4-n. The branching device 4-n distributes the optical signal relayed by the relay device 3-n to a plurality of receiving devices 5-n.
　以下、受信装置５－ｎに入力される光信号の強度レベルの下限は「Ｐｄｎ」と表記される。以下、受信装置５－ｎに入力される光信号の強度レベルの上限は「Ｐｕｎ」と表記される。 　Hereinafter, the lower limit of the intensity level of the optical signal input to the receiving device 5-n is denoted as "Pdn". Hereinafter, the upper limit of the intensity level of the optical signal input to the receiving device 5-n is expressed as "Pun".
　受信装置５は、光加入者線終端装置（ONU）である。以下では、受信装置５は、映像信号を出力する光加入者線終端装置（V-ONU）である。受信装置５－ｎには、所定の強度レベル［ｄＢｍ］を有する光信号が、分岐装置４－ｎから入力される。例えば、受信装置５－１には、伝送距離に応じて、「Ｐｄ１」から「Ｐｕ１」までの幅の強度レベルを有する光信号が、分岐装置４－１から入力される。例えば、受信装置５－２には、伝送距離に応じて、「Ｐｄ２」から「Ｐｕ２」までの幅の強度レベルを有する光信号が、分岐装置４－２から入力される。 The receiving device 5 is an optical network unit (ONU). In the following, the receiving device 5 is an optical network unit (V-ONU) that outputs video signals. An optical signal having a predetermined intensity level [dBm] is input from the branching device 4-n to the receiving device 5-n. For example, an optical signal having an intensity level ranging from "Pd1" to "Pu1" depending on the transmission distance is input from the branching device 4-1 to the receiving device 5-1. For example, an optical signal having an intensity level ranging from "Pd2" to "Pu2" depending on the transmission distance is input from the branching device 4-2 to the receiving device 5-2.
　受信装置５－ｎは、分岐装置４－ｎから入力された光信号に応じた電気信号に対して復調処理を実行することによって、搬送波信号を電気信号に基づいて生成する。受信装置５は、生成された搬送波信号を、ユーザ端末（不図示）に出力する。ユーザ端末は、例えば、映像を再生する情報処理装置である。 The receiving device 5-n generates a carrier wave signal based on the electrical signal by executing demodulation processing on the electrical signal corresponding to the optical signal input from the branching device 4-n. The receiving device 5 outputs the generated carrier signal to a user terminal (not shown). A user terminal is, for example, an information processing device that reproduces video.
　次に、受信装置５ａの詳細を説明する。
　図２は、第１実施形態における、受信装置５ａの構成例を示す図である。受信装置５ａは、図１に示された受信装置５に対応する。受信装置５ａは、レベル測定部５０と、物理量測定部５１ａと、制御部５２ａと、レベル増幅部５３ａと、光学処理部５４ａと、復調部５５と、搬送波信号増幅部５６ａとを備える。光学処理部５４ａは、変換部５４０と、分岐部５４１と、プリアンプ５４２とを備える。搬送波信号増幅部５６ａは、濾波器５６０と、ポストアンプ５６１とを備える。 Next, the details of the receiving device 5a will be described.
FIG. 2 is a diagram showing a configuration example of the receiving device 5a in the first embodiment. The receiving device 5a corresponds to the receiving device 5 shown in FIG. The receiver 5a includes a level measuring section 50, a physical quantity measuring section 51a, a control section 52a, a level amplifying section 53a, an optical processing section 54a, a demodulating section 55, and a carrier wave signal amplifying section 56a. The optical processing section 54 a includes a conversion section 540 , a branch section 541 and a preamplifier 542 . The carrier wave signal amplifying section 56 a includes a filter 560 and a post-amplifier 561 .
　光学処理部５４ａは、分岐部５４１の前段及び後段の少なくとも一方に、電気アンプを更に備えてもよい。これによって、分岐部５４１による電気信号の分岐に伴って電気信号の強度レベルが低下した場合でも、電気信号の強度レベルを補償することができる。 The optical processing section 54a may further include an electric amplifier in at least one of the front stage and the rear stage of the branch section 541. This makes it possible to compensate for the intensity level of the electrical signal even when the intensity level of the electrical signal is lowered due to the branching of the electrical signal by the branching unit 541 .
　レベル測定部５０は、光信号が分岐装置４から入力される。レベル測定部５０は、分岐装置４から入力された光信号の強度レベルを測定する。レベル測定部５０は、測定された光信号の強度レベルを表す制御信号を、制御部５２ａに出力する。レベル測定部５０は、分岐装置４から入力された光信号を、レベル増幅部５３ａに出力する。 The optical signal is input from the branching device 4 to the level measurement unit 50 . The level measuring section 50 measures the intensity level of the optical signal input from the branching device 4 . The level measuring section 50 outputs a control signal representing the measured intensity level of the optical signal to the control section 52a. The level measuring section 50 outputs the optical signal input from the branching device 4 to the level amplifying section 53a.
　物理量測定部５１ａには、電気信号（周波数変調一括変換信号）が、分岐部５４１から入力される。以下、周波数変調一括変換信号は「ＦＭ一括変換信号」と表記される。物理量測定部５１ａは、分岐部５４１から入力された電気信号（ＦＭ一括変換信号）の強度レベルを測定する。物理量測定部５１ａは、測定された電気信号（ＦＭ一括変換信号）の強度レベルを表す制御信号を、制御部５２ａに出力する。 An electrical signal (frequency-modulated batch-converted signal) is input from the branching section 541 to the physical quantity measuring section 51a. Hereinafter, the frequency-modulated batch-converted signal will be referred to as "FM batch-converted signal". The physical quantity measuring unit 51a measures the strength level of the electrical signal (FM batch conversion signal) input from the branching unit 541 . The physical quantity measurement unit 51a outputs a control signal representing the intensity level of the measured electrical signal (FM batch conversion signal) to the control unit 52a.
　制御部５２ａは、光信号の強度レベル「Ｐｍ」を表す制御信号を、レベル測定部５０から取得する。制御部５２ａは、電気信号（ＦＭ一括変換信号）の強度レベル「Ｅｍ」を表す制御信号を、物理量測定部５１ａから取得する。 The control unit 52a acquires from the level measurement unit 50 a control signal representing the intensity level "Pm" of the optical signal. The control unit 52a acquires the control signal representing the intensity level "Em" of the electrical signal (FM batch conversion signal) from the physical quantity measurement unit 51a.
　制御部５２ａは、変換部５４０が受光可能な光信号の強度レベルの範囲「Ｐｄ～Ｐｕ」［ｄＢｍ］を表すデータと、復調部５５が実行する復調処理に必要とされる電気信号の強度レベル「Ｅ」を表すデータとを、予め保持している。 The control unit 52a receives data representing the range “Pd to Pu” [dBm] of the intensity level of the optical signal that can be received by the conversion unit 540, and the intensity level of the electrical signal required for the demodulation processing executed by the demodulation unit 55. Data representing "E" is stored in advance.
　制御部５２ａは、電気信号の強度レベル「Ｅｍ」が強度レベル「Ｅ」以上となり、かつ、変換部５４０に入力される光信号の強度レベルが下限「Ｐｄ」から上限「Ｐｕ」までの範囲に収まるように、レベル増幅部５３ａにおける光信号の増幅ゲインを調整する。制御部５２ａは、増幅ゲインを表す制御信号を、レベル増幅部５３ａに出力する。 The control unit 52a controls the intensity level “Em” of the electric signal to be equal to or higher than the intensity level “E” and the intensity level of the optical signal input to the conversion unit 540 to be within the range from the lower limit “Pd” to the upper limit “Pu”. The amplification gain of the optical signal in the level amplifier 53a is adjusted so as to be contained. The control section 52a outputs a control signal representing the amplification gain to the level amplification section 53a.
　制御部５２ａは、電気信号の強度レベル「Ｅ」よりも電気信号の強度レベル「Ｅｍ」が低いか否かを判定する。制御部５２ａは、電気信号の強度レベル「Ｅ」よりも電気信号の強度レベル「Ｅｍ」が低い場合、光信号の強度レベル「Ｐｍ」よりも一定幅「Ｐｗ」だけ高い強度レベルの光信号をレベル増幅部５３ａが変換部５４０に出力するように、レベル増幅部５３ａにおける光信号の増幅ゲインを調整する。 The control unit 52a determines whether the intensity level "Em" of the electric signal is lower than the intensity level "E" of the electric signal. When the intensity level "Em" of the electric signal is lower than the intensity level "E" of the electric signal, the control unit 52a outputs an optical signal having an intensity level higher than the intensity level "Pm" of the optical signal by a certain width "Pw". The amplification gain of the optical signal in the level amplification section 53 a is adjusted so that the level amplification section 53 a outputs to the conversion section 540 .
　制御部５２ａは、電気信号の強度レベル「Ｅ」よりも電気信号の強度レベル「Ｅｍ」が低いか否かを、再度判定する。制御部５２ａは、必要とされる電気信号の強度レベル「Ｅ」よりも電気信号の強度レベル「Ｅｍ」が低い場合、レベル増幅部５３ａにおける光信号の増幅ゲインを再調整する。制御部５２ａは、電気信号の強度レベル「Ｅｍ」が電気信号の強度レベル「Ｅ」以上であると判定されるまで、レベル増幅部５３ａにおける光信号の増幅ゲインを再調整する。ただし、光信号の強度レベルが上限「Ｐｕ」を上回る場合には、制御部５２ａは、光信号の強度レベルが上限「Ｐｕ」を上回らないように、増幅ゲインの再調整処理を中止する。 The control unit 52a determines again whether the intensity level "Em" of the electric signal is lower than the intensity level "E" of the electric signal. When the electric signal intensity level "Em" is lower than the required electric signal intensity level "E", the control unit 52a readjusts the amplification gain of the optical signal in the level amplifying unit 53a. The controller 52a readjusts the amplification gain of the optical signal in the level amplifier 53a until it is determined that the intensity level "Em" of the electrical signal is equal to or higher than the intensity level "E" of the electrical signal. However, if the intensity level of the optical signal exceeds the upper limit "Pu", the controller 52a stops the amplification gain readjustment process so that the intensity level of the optical signal does not exceed the upper limit "Pu".
　制御部５２ａが実行する制御のアルゴリズムは、特定のアルゴリズムに限定されない。制御部５２ａは、例えば二分探索法又は非線形最小二乗法等の最適化手法を用いて、増幅ゲインの調整処理を実行する。なお、搬送波信号の品質（例えば、搬送波対雑音比）が映像再生可能な品質基準（閾値）に達しているのであれば、電気信号の強度レベル「Ｅｍ」は、最適化されていなくてもよい。 The control algorithm executed by the control unit 52a is not limited to a specific algorithm. The control unit 52a executes amplification gain adjustment processing using, for example, an optimization method such as a binary search method or a nonlinear least-squares method. It should be noted that the electrical signal strength level "Em" may not be optimized if the quality of the carrier signal (e.g. carrier-to-noise ratio) reaches a quality criterion (threshold) for video reproduction. .
　レベル増幅部５３ａ（可変増幅部）には、搬送波信号に応じた光信号が、レベル測定部５０から入力される。レベル増幅部５３ａは、増幅ゲインを表す制御信号を、制御部５２ａから取得する。レベル増幅部５３ａは、制御信号を用いて指示された増幅ゲインに基づいて、光信号の強度レベルを増幅させる。レベル増幅部５３ａは、光信号を変換部５４０に出力する。 An optical signal corresponding to the carrier wave signal is input from the level measuring section 50 to the level amplifying section 53a (variable amplifying section). The level amplifier 53a acquires a control signal representing an amplification gain from the controller 52a. The level amplifier 53a amplifies the intensity level of the optical signal based on the amplification gain instructed using the control signal. The level amplifier 53 a outputs the optical signal to the converter 540 .
　光学処理部５４ａは、例えば、レシーバ光サブアセンブリ（Receiver Optical Sub-Assembly : ROSA）である。変換部５４０（光電変換部）は、フォトダイオードである。変換部５４０には、光信号がレベル増幅部５３ａから入力される。変換部５４０は、光信号を電気信号（ＦＭ一括変換信号）に変換する。変換部５４０は、変換された電気信号を分岐部５４１に出力する。 The optical processing unit 54a is, for example, a receiver optical sub-assembly (ROSA). The conversion unit 540 (photoelectric conversion unit) is a photodiode. An optical signal is input to the converter 540 from the level amplifier 53a. The converter 540 converts the optical signal into an electrical signal (FM batch conversion signal). Conversion unit 540 outputs the converted electrical signal to branch unit 541 .
　分岐部５４１は、電気信号を変換部５４０から取得する。分岐部５４１は、電気信号（ＦＭ一括変換信号）を、プリアンプ５４２と物理量測定部５１ａとに分配する。 The branching unit 541 acquires the electrical signal from the conversion unit 540. The branching unit 541 distributes the electric signal (FM batch conversion signal) to the preamplifier 542 and the physical quantity measuring unit 51a.
　プリアンプ５４２は、例えば、トランスインピーダンス・アンプ（Trans-impedance amplifier : TIA）である。プリアンプ５４２は、電気信号（ＦＭ一括変換信号）を、分岐部５４１から取得する。プリアンプ５４２は、予め定められた増幅ゲインに基づいて、電気信号の強度レベルを増幅させる。プリアンプ５４２は、強度レベルが「Ｅ」以上である電気信号を、復調部５５に出力する。 The preamplifier 542 is, for example, a trans-impedance amplifier (TIA). The preamplifier 542 acquires the electrical signal (FM batch conversion signal) from the branch section 541 . Preamplifier 542 amplifies the intensity level of the electrical signal based on a predetermined amplification gain. The preamplifier 542 outputs to the demodulator 55 an electrical signal with an intensity level of “E” or higher.
　復調部５５は、強度レベルが「Ｅ」以上である電気信号（ＦＭ一括変換信号）を、プリアンプ５４２から取得する。復調部５５は、電気信号（ＦＭ一括変換信号）に対して復調処理を実行することによって、搬送波信号（映像信号）を電気信号に基づいて生成する。復調部５５は、搬送波信号を濾波器５６０に出力する。 The demodulator 55 acquires from the preamplifier 542 an electrical signal (FM batch-converted signal) whose intensity level is "E" or higher. The demodulator 55 generates a carrier wave signal (video signal) based on the electrical signal by performing demodulation processing on the electrical signal (FM batch conversion signal). Demodulator 55 outputs the carrier signal to filter 560 .
　搬送波信号増幅部５６ａは、搬送波信号の強度レベルを増幅する。濾波器５６０は、搬送波信号（映像信号）を、復調部５５から取得する。濾波器５６０は、低域通過濾波器（Low-pass filter : LPF）である。濾波器５６０は、低域の搬送波信号（映像信号）を通過させる。すなわち、濾波器５６０は、搬送波信号（映像信号）からノイズを除去する。ポストアンプ５６１は、予め定められた増幅ゲインに基づいて、ノイズが除去された搬送波信号（映像信号）の強度レベルを増幅させる。ポストアンプ５６１は、強度レベルが増幅された搬送波信号（映像信号）を、ユーザ端末（不図示）に出力する。 The carrier wave signal amplifier 56a amplifies the strength level of the carrier wave signal. Filter 560 acquires the carrier wave signal (video signal) from demodulator 55 . Filter 560 is a low-pass filter (LPF). The filter 560 passes the low frequency carrier wave signal (video signal). That is, the filter 560 removes noise from the carrier signal (video signal). The post-amplifier 561 amplifies the intensity level of the noise-removed carrier wave signal (video signal) based on a predetermined amplification gain. The post-amplifier 561 outputs a carrier wave signal (video signal) whose intensity level is amplified to a user terminal (not shown).
　このように、強度レベルが増幅された搬送波信号の品質は、所定の閾値以上である。すなわち、搬送波信号では、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とが保証されている。 Thus, the quality of the carrier signal whose intensity level is amplified is above the predetermined threshold. That is, the carrier signal has a guaranteed carrier-to-noise ratio, an amount of complex second-order distortion, and an amount of complex third-order distortion.
　次に、光伝送システム１の動作例を説明する。
　図３は、第１実施形態における、光伝送システム１の動作例を示すフローチャートである。光伝送システム１は、図３にフローチャートを用いて示された動作を、所定周期で実行する。 Next, an operation example of the optical transmission system 1 will be described.
FIG. 3 is a flow chart showing an operation example of the optical transmission system 1 in the first embodiment. The optical transmission system 1 performs the operation shown using the flowchart in FIG. 3 at predetermined intervals.
　レベル測定部５０は、入力された光信号の強度レベルを測定する。レベル増幅部５３ａは、制御信号を用いて制御部５２ａから指示された増幅ゲインに基づいて、光信号の強度レベルを増幅させる（ステップＳ１０１）。変換部５４０は、光信号を電気信号（ＦＭ一括変換信号）に変換する。分岐部５４１は、電気信号（ＦＭ一括変換信号）を、プリアンプ５４２と物理量測定部５１ａとに分配する。物理量測定部５１ａは、分岐部５４１から入力された電気信号（ＦＭ一括変換信号）の強度レベルを測定する（ステップＳ１０２）。 The level measurement unit 50 measures the intensity level of the input optical signal. The level amplifier 53a amplifies the intensity level of the optical signal based on the amplification gain instructed by the controller 52a using the control signal (step S101). The converter 540 converts the optical signal into an electrical signal (FM batch conversion signal). The branching unit 541 distributes the electric signal (FM batch conversion signal) to the preamplifier 542 and the physical quantity measuring unit 51a. The physical quantity measuring unit 51a measures the intensity level of the electrical signal (FM batch conversion signal) input from the branching unit 541 (step S102).
　物理量測定部５１ａは、分岐部５４１から入力された電気信号（ＦＭ一括変換信号）の強度レベルを測定する（ステップＳ１０３）。制御部５２ａは、電気信号の強度レベル「Ｅｍ」が電気信号の強度レベル「Ｅ」以上（閾値以上）であるか否かを判定する（ステップＳ１０４）。電気信号の強度レベル「Ｅｍ」が電気信号の強度レベル「Ｅ」以上であると判定された場合（ステップＳ１０４：ＹＥＳ）、光伝送システム１は、図３にフローチャートを用いて示された動作を終了する。 The physical quantity measuring unit 51a measures the intensity level of the electrical signal (FM batch conversion signal) input from the branching unit 541 (step S103). The control unit 52a determines whether or not the electric signal strength level "Em" is equal to or higher than the electric signal strength level "E" (threshold value or higher) (step S104). When it is determined that the electric signal intensity level "Em" is equal to or higher than the electric signal intensity level "E" (step S104: YES), the optical transmission system 1 performs the operation shown using the flowchart in FIG. finish.
　電気信号の強度レベル「Ｅｍ」が電気信号の強度レベル「Ｅ」未満であると判定された場合（ステップＳ１０４：ＮＯ）、制御部５２ａは、レベル増幅部５３ａが光信号の強度レベルを一定幅「Ｐｗ」だけ更に増幅させるように、制御信号を生成する。レベル増幅部５３ａは、光信号の強度レベルを一定幅「Ｐｗ」だけ更に増幅させる（ステップＳ１０５）。 When it is determined that the electric signal intensity level “Em” is less than the electric signal intensity level “E” (step S104: NO), the control unit 52a causes the level amplifying unit 53a to increase the optical signal intensity level by a certain width. A control signal is generated to further amplify by "Pw". The level amplifier 53a further amplifies the intensity level of the optical signal by a certain width "Pw" (step S105).
　制御部５２ａは、一定幅「Ｐｗ」だけ更に増幅された強度レベルが上限「Ｐｕ」を上回るか否かを判定する（ステップＳ１０６）。一定幅「Ｐｗ」だけ更に増幅された強度レベルが上限「Ｐｕ」以下であると判定された場合（ステップＳ１０６：ＮＯ）、光伝送システム１は、図３にフローチャートを用いて示された動作を終了する。一定幅「Ｐｗ」だけ更に増幅された強度レベルが上限「Ｐｕ」を上回ると判定された場合（ステップＳ１０６：ＹＥＳ）、制御部５２ａは、レベル増幅部５３ａが光信号の強度レベルを一定幅だけ更に増幅する処理を中止するように、制御信号を生成する。レベル増幅部５３ａは、光信号の強度レベルを、上限の増幅ゲインで増幅させる（ステップＳ１０７）。 The control unit 52a determines whether or not the intensity level further amplified by the constant width "Pw" exceeds the upper limit "Pu" (step S106). If it is determined that the intensity level further amplified by the constant width "Pw" is equal to or lower than the upper limit "Pu" (step S106: NO), the optical transmission system 1 performs the operation shown using the flowchart in FIG. finish. If it is determined that the intensity level further amplified by the constant width "Pw" exceeds the upper limit "Pu" (step S106: YES), the control unit 52a causes the level amplifier 53a to increase the intensity level of the optical signal by the constant width. A control signal is generated to stop the process of further amplification. The level amplifier 53a amplifies the intensity level of the optical signal with the upper limit amplification gain (step S107).
　以上のように、変換部５４０は、受信された光信号（ＦＭ一括変換信号）を電気信号に変換する。復調部５５は、電気信号に基づいて搬送波信号を生成する。物理量測定部５１ａは、変換部５４０から出力された電気信号の物理量を測定する。制御部５２ａは、電気信号の物理量（強度レベル「Ｅｍ」）が第１閾値（強度レベル「Ｅ」）未満である場合、受信された光信号の物理量を調整する。例えば、電気信号の物理量は、電気信号の強度レベルである。制御部５２ａは、電気信号の物理量が第１閾値未満である場合、受信された光信号の強度レベルを増幅させる。 As described above, the conversion unit 540 converts the received optical signal (FM batch conversion signal) into an electrical signal. A demodulator 55 generates a carrier wave signal based on the electrical signal. The physical quantity measuring section 51 a measures the physical quantity of the electrical signal output from the converting section 540 . The controller 52a adjusts the physical quantity of the received optical signal when the physical quantity (intensity level "Em") of the electrical signal is less than the first threshold (intensity level "E"). For example, the physical quantity of the electrical signal is the intensity level of the electrical signal. The controller 52a amplifies the intensity level of the received optical signal when the physical quantity of the electrical signal is less than the first threshold.
　これによって、伝送距離ごとに異なる受信性能の受信装置が用意されなくても、搬送波信号の品質を向上させることが可能である。すなわち、伝送距離に応じて受信装置が使い分けられなくても、搬送波信号の品質を向上させることが可能である。 As a result, it is possible to improve the quality of carrier signals without preparing receivers with different reception performance for different transmission distances. That is, it is possible to improve the quality of the carrier wave signal even if the receiving device cannot be used properly according to the transmission distance.
　第１実施形態では、受信装置５ａは、入力された光信号の強度レベルを調整することによって、出力される搬送波信号の品質を改善する。これによって、中継装置３－ｎと受信装置５ａとの間の伝送距離を長くすることができるので、より広いエリアにおいて同じ受信性能の受信装置５ａを使用することが可能である。 In the first embodiment, the receiving device 5a improves the quality of the output carrier signal by adjusting the intensity level of the input optical signal. As a result, the transmission distance between the relay device 3-n and the receiving device 5a can be increased, so that the receiving device 5a with the same reception performance can be used in a wider area.
　搬送波対雑音比（CNR）の劣化には、光信号の伝送路における雑音と、受信装置５ａ（V-ONU）の内部における雑音との両方が影響する。受信装置５ａに入力される光信号の強度レベルが低い場合には、受信装置５ａの内部における雑音の影響が、光信号の伝送路における雑音の影響よりも大きい。そのため、受信装置５ａに入力される光信号の強度レベルが増幅されることによって、受信装置５ａの内部における雑音の影響が緩和されるので、搬送波対雑音比（CNR）の劣化を抑制することが可能である。 Degradation of the carrier-to-noise ratio (CNR) is affected by both noise in the optical signal transmission path and noise inside the receiver 5a (V-ONU). When the intensity level of the optical signal input to the receiver 5a is low, the influence of noise inside the receiver 5a is greater than the influence of noise in the transmission line of the optical signal. Therefore, by amplifying the intensity level of the optical signal input to the receiving device 5a, the influence of noise inside the receiving device 5a is alleviated, so deterioration of the carrier-to-noise ratio (CNR) can be suppressed. It is possible.
　（第２実施形態）
　第２実施形態では、ポストアンプから出力された搬送波信号（映像信号）の品質が測定される点が、第１実施形態との差分である。第２実施形態では、第１実施形態との差分を中心に説明する。 (Second embodiment)
The second embodiment differs from the first embodiment in that the quality of the carrier wave signal (video signal) output from the postamplifier is measured. 2nd Embodiment demonstrates centering around the difference with 1st Embodiment.
　図４は、第２実施形態における、受信装置５ｂの構成例を示す図である。受信装置５ｂは、図１に示された受信装置５に対応する。受信装置５ｂは、レベル測定部５０と、物理量測定部５１ｂと、制御部５２ｂと、レベル増幅部５３ｂと、光学処理部５４ｂと、復調部５５と、搬送波信号増幅部５６ｂとを備える。 FIG. 4 is a diagram showing a configuration example of the receiving device 5b in the second embodiment. The receiving device 5b corresponds to the receiving device 5 shown in FIG. The receiver 5b includes a level measuring section 50, a physical quantity measuring section 51b, a control section 52b, a level amplifying section 53b, an optical processing section 54b, a demodulating section 55, and a carrier wave signal amplifying section 56b.
　制御部５２ｂと、レベル増幅部５３ｂと、光学処理部５４ｂとは、図２に示された制御部５２ａと、レベル増幅部５３ａと、光学処理部５４ａとに対応する。光学処理部５４ｂは、変換部５４０と、プリアンプ５４２とを備える。搬送波信号増幅部５６ｂは、濾波器５６０と、ポストアンプ５６１と、分岐部５６２とを備える。 The control section 52b, the level amplification section 53b, and the optical processing section 54b correspond to the control section 52a, the level amplification section 53a, and the optical processing section 54a shown in FIG. The optical processing section 54 b includes a conversion section 540 and a preamplifier 542 . The carrier wave signal amplifying section 56b includes a filter 560, a post-amplifier 561, and a branching section 562. FIG.
　搬送波信号増幅部５６ｂは、分岐部５６２の前段及び後段の少なくとも一方に、電気アンプを更に備えてもよい。これによって、分岐部５６２による電気信号の分岐に伴って電気信号の強度レベルが低下した場合でも、電気信号の強度レベルを補償することができる。 The carrier wave signal amplification section 56b may further include an electric amplifier in at least one of the front stage and the rear stage of the branch section 562. As a result, even if the intensity level of the electrical signal is lowered due to branching of the electrical signal by the branching unit 562, the intensity level of the electrical signal can be compensated.
　物理量測定部５１ｂには、電気信号（映像信号）が分岐部５６２から入力される。物理量測定部５１ｂは、分岐部５６２から入力された電気信号（映像信号）の搬送波対雑音比（CNR）を測定する。物理量測定部５１ｂは、分岐部５６２から入力された電気信号の複合２次歪の量と複合３次歪の量とを測定してもよい。物理量測定部５１ｂは、測定された電気信号（映像信号）の搬送波対雑音比「ＣＮＲｍ（ｉ）」を表す制御信号を、制御部５２ｂに出力する。この符号「ｉ」は、整数「Ｎ」が映像チャネルの総数を表す場合、０よりも大きく、整数「Ｎ」よりも小さい整数である。 An electric signal (video signal) is input from the branching unit 562 to the physical quantity measuring unit 51b. The physical quantity measuring unit 51b measures the carrier-to-noise ratio (CNR) of the electrical signal (video signal) input from the branching unit 562. FIG. The physical quantity measurement unit 51 b may measure the amount of complex second-order distortion and the amount of complex third-order distortion of the electrical signal input from the branching unit 562 . The physical quantity measuring unit 51b outputs a control signal representing the measured carrier-to-noise ratio “CNRm(i)” of the electrical signal (video signal) to the control unit 52b. The code 'i' is an integer greater than 0 and less than the integer 'N', where the integer 'N' represents the total number of video channels.
　制御部５２ｂは、光信号の強度レベル「Ｐｍ」を表す制御信号を、レベル測定部５０から取得する。制御部５２ｂは、電気信号（映像信号）の搬送波対雑音比を表す制御信号を、物理量測定部５１ｂから取得する。 The control unit 52b acquires from the level measurement unit 50 a control signal representing the intensity level "Pm" of the optical signal. The control unit 52b acquires a control signal representing the carrier-to-noise ratio of the electric signal (video signal) from the physical quantity measurement unit 51b.
　制御部５２ｂは、変換部５４０が受光可能な光信号の強度レベルの範囲「Ｐｄ～Ｐｕ」［ｄＢｍ］を表すデータと、映像再生に必要とされる電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」を表すデータとを、予め保持している。 The control unit 52b provides data representing the range of intensity levels of optical signals that the conversion unit 540 can receive, “Pd to Pu” [dBm], and the carrier-to-noise ratio “CNR(i )” is stored in advance.
　制御部５２ｂは、電気信号の強度レベル「Ｅｍ」が強度レベル「Ｅ」以上となり、かつ、変換部５４０に入力される光信号の強度レベルが下限「Ｐｄ」から上限「Ｐｕ」までの範囲に収まるように、レベル増幅部５３ｂにおける光信号の増幅ゲインを調整する。制御部５２ｂは、増幅ゲインを表す制御信号を、レベル増幅部５３ｂに出力する。 The control unit 52b controls the intensity level “Em” of the electric signal to be equal to or higher than the intensity level “E” and the intensity level of the optical signal input to the conversion unit 540 to be within the range from the lower limit “Pd” to the upper limit “Pu”. The amplification gain of the optical signal in the level amplification unit 53b is adjusted so as to be contained. The control section 52b outputs a control signal representing the amplification gain to the level amplification section 53b.
　制御部５２ｂは、電気信号（映像信号）の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が低いか否かを判定する。制御部５２ｂは、電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が低い場合、光信号の強度レベル「Ｐｍ」よりも一定幅「Ｐｗ」だけ高い強度レベルの光信号をレベル増幅部５３ｂが変換部５４０に出力するように、レベル増幅部５３ｂにおける光信号の増幅ゲインを調整する。 The control unit 52b determines whether or not the carrier-to-noise ratio "CNRm(i)" of the electrical signal (video signal) is lower than the carrier-to-noise ratio "CNR(i)" of the electrical signal (video signal). When the carrier-to-noise ratio “CNRm(i)” of the electrical signal is lower than the carrier-to-noise ratio “CNR(i)” of the electrical signal, the control unit 52b controls the control unit 52b to set the power level “Pm” of the optical signal to a certain width “ The amplification gain of the optical signal in the level amplification section 53b is adjusted so that the level amplification section 53b outputs an optical signal having an intensity level higher by "Pw" to the conversion section 540. FIG.
　制御部５２ｂは、電気信号（映像信号）の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が低いか否かを再度判定する。制御部５２ｂは、必要とされる電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が低い場合、レベル増幅部５３ｂにおける光信号の増幅ゲインを再調整する。制御部５２ｂは、電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」以上であると判定されるまで、レベル増幅部５３ｂにおける光信号の増幅ゲインを再調整する。ただし、光信号の強度レベルが上限「Ｐｕ」を上回る場合には、制御部５２ｂは、光信号の強度レベルが上限「Ｐｕ」を上回らないように、増幅ゲインの再調整処理を中止する。また、光信号の強度レベルが下限「Ｐｄ」を下回る場合には、制御部５２ｂは、光信号の強度レベルが下限「Ｐｄ」を下回らないように、増幅ゲインの再調整処理を中止する。 The control unit 52b determines again whether the carrier-to-noise ratio "CNRm(i)" of the electrical signal is lower than the carrier-to-noise ratio "CNR(i)" of the electrical signal (video signal). When the carrier-to-noise ratio "CNRm(i)" of the electrical signal is lower than the required carrier-to-noise ratio "CNR(i)" of the electrical signal, the control unit 52b amplifies the optical signal in the level amplifier 53b. Readjust the gain. The controller 52b amplifies the optical signal in the level amplifier 53b until it is determined that the carrier-to-noise ratio "CNRm(i)" of the electrical signal is greater than or equal to the carrier-to-noise ratio "CNR(i)" of the electrical signal. Readjust the gain. However, if the intensity level of the optical signal exceeds the upper limit "Pu", the controller 52b stops the amplification gain readjustment process so that the intensity level of the optical signal does not exceed the upper limit "Pu". Further, when the intensity level of the optical signal falls below the lower limit "Pd", the controller 52b stops the amplification gain readjustment process so that the intensity level of the optical signal does not fall below the lower limit "Pd".
　制御部５２ｂが実行する制御のアルゴリズムは、特定のアルゴリズムに限定されない。制御部５２ｂは、例えば二分探索法又は非線形最小二乗法等の最適化手法を用いて、増幅ゲインの調整処理を実行する。なお、搬送波信号の品質（例えば、搬送波対雑音比）が映像再生可能な品質基準（閾値）に達しているのであれば、電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」は、最適化されていなくてもよい。 The control algorithm executed by the control unit 52b is not limited to a specific algorithm. The control unit 52b executes amplification gain adjustment processing using an optimization method such as a binary search method or a nonlinear least-squares method. Note that if the quality of the carrier signal (e.g., carrier-to-noise ratio) reaches a quality standard (threshold) that allows video reproduction, the carrier-to-noise ratio "CNRm(i)" of the electrical signal is optimized. It doesn't have to be.
　レベル増幅部５３ｂ（可変増幅部）には、搬送波信号に応じた光信号が、レベル測定部５０から入力される。レベル増幅部５３ｂは、増幅ゲインを表す制御信号を、制御部５２ｂから取得する。レベル増幅部５３ｂは、制御信号を用いて指示された増幅ゲインに基づいて、光信号の強度レベルを増幅させる。レベル増幅部５３ｂは、光信号を変換部５４０に出力する。 An optical signal corresponding to the carrier signal is input from the level measuring section 50 to the level amplifying section 53b (variable amplifying section). The level amplifier 53b acquires the control signal representing the amplification gain from the controller 52b. The level amplifier 53b amplifies the intensity level of the optical signal based on the amplification gain instructed using the control signal. The level amplifier 53 b outputs the optical signal to the converter 540 .
　光学処理部５４ｂは、例えば、レシーバ光サブアセンブリである。変換部５４０には、光信号がレベル増幅部５３ｂから入力される。変換部５４０は、光信号を電気信号（ＦＭ一括変換信号）に変換する。変換部５４０は、変換された電気信号をプリアンプ５４２に出力する。 The optical processor 54b is, for example, a receiver optical subassembly. An optical signal is input to the converter 540 from the level amplifier 53b. The converter 540 converts the optical signal into an electrical signal (FM batch conversion signal). Conversion unit 540 outputs the converted electrical signal to preamplifier 542 .
　ポストアンプ５６１は、強度レベルが増幅された搬送波信号（映像信号）を、分岐部５６２に出力する。分岐部５６２は、搬送波信号（映像信号）をポストアンプ５６１から取得する。分岐部５６２は、搬送波信号（映像信号）を、ユーザ端末（不図示）と物理量測定部５１ｂとに分配する。 The post-amplifier 561 outputs the carrier wave signal (video signal) whose intensity level is amplified to the branching unit 562 . The branching unit 562 acquires the carrier wave signal (video signal) from the post-amplifier 561 . The branching unit 562 distributes the carrier wave signal (video signal) to the user terminal (not shown) and the physical quantity measuring unit 51b.
　次に、光伝送システム１の動作例を説明する。
　図５は、第２実施形態における、光伝送システム１の動作例を示すフローチャートである。光伝送システム１は、図５にフローチャートを用いて示された動作を、所定周期で実行する。ステップＳ２０１からステップＳ２０２までの動作は、図３に示されたステップＳ１０１からステップＳ１０２までの動作と同様である。 Next, an operation example of the optical transmission system 1 will be described.
FIG. 5 is a flow chart showing an operation example of the optical transmission system 1 in the second embodiment. The optical transmission system 1 performs the operation shown using the flowchart in FIG. 5 at predetermined intervals. The operations from step S201 to step S202 are the same as the operations from step S101 to step S102 shown in FIG.
　復調部５５は、電気信号（ＦＭ一括変換信号）に対して復調処理を実行することによって、搬送波信号（映像信号）を電気信号に基づいて生成する（ステップＳ２０３）。物理量測定部５１ｂは、分岐部５６２から入力された電気信号の搬送波対雑音比（CNR）と、搬送波信号の複合２次歪の量と、搬送波信号の複合３次歪の量とのうちの少なくとも一つを測定する（ステップＳ２０４）。 The demodulator 55 generates a carrier wave signal (video signal) based on the electrical signal by performing demodulation processing on the electrical signal (FM batch conversion signal) (step S203). The physical quantity measuring unit 51b measures at least one of the carrier-to-noise ratio (CNR) of the electrical signal input from the branching unit 562, the amount of complex second-order distortion of the carrier signal, and the amount of complex third-order distortion of the carrier signal. One is measured (step S204).
　制御部５２ｂは、例えば、搬送波雑音比が搬送波信号の閾値以上（品質基準以上）であるか否かを判定する（ステップＳ２０５）。搬送波雑音比が搬送波信号の閾値以上（品質基準以上）であると判定された場合（ステップＳ２０５：ＹＥＳ）、光伝送システム１は、図５にフローチャートを用いて示された動作を終了する。 For example, the control unit 52b determines whether the carrier-to-noise ratio is equal to or higher than the threshold value of the carrier signal (equal to or higher than the quality standard) (step S205). If it is determined that the carrier-to-noise ratio is greater than or equal to the threshold value of the carrier signal (ie, greater than or equal to the quality standard) (step S205: YES), the optical transmission system 1 terminates the operation shown using the flowchart in FIG.
　搬送波雑音比が搬送波信号の閾値未満（品質基準未満）であると判定された場合（ステップＳ２０５：ＮＯ）、制御部５２ｂは、ステップＳ２０６に処理を進める。ステップＳ２０６からステップＳ２０８までの動作は、図３に示されたステップＳ１０５からステップＳ１０７までの動作と同様である。 If it is determined that the carrier-to-noise ratio is less than the carrier signal threshold (less than the quality standard) (step S205: NO), the control unit 52b proceeds to step S206. The operations from step S206 to step S208 are the same as the operations from step S105 to step S107 shown in FIG.
　以上のように、変換部５４０は、受信された光信号を電気信号に変換する。復調部５５は、電気信号に基づいて搬送波信号を生成する。物理量測定部５１ｂは、ポストアンプ５６１から出力された搬送波信号の物理量を測定する。搬送波信号の物理量は、例えば、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とのうちの少なくとも一つである。制御部５２ｂは、搬送波信号の物理量が第２閾値未満（品質基準未満）である場合、受信された光信号の物理量を調整する。例えば、制御部５２ｂは、搬送波信号の物理量が第２閾値未満である場合、受信された光信号の強度レベルを増幅させる。 As described above, the conversion unit 540 converts the received optical signal into an electrical signal. A demodulator 55 generates a carrier wave signal based on the electrical signal. The physical quantity measuring section 51b measures the physical quantity of the carrier wave signal output from the post-amplifier 561. FIG. The physical quantity of the carrier signal is, for example, at least one of the carrier-to-noise ratio, the amount of composite second-order distortion, and the amount of composite third-order distortion. The controller 52b adjusts the physical quantity of the received optical signal when the physical quantity of the carrier signal is less than the second threshold (less than the quality standard). For example, the controller 52b amplifies the intensity level of the received optical signal when the physical quantity of the carrier signal is less than the second threshold.
　これによって、伝送距離ごとに異なる受信性能の受信装置が用意されなくても、搬送波信号の品質を更に向上させることが可能である。また、電気信号（周波数変調一括変換信号）の強度レベル「Ｅｍ」が最初から強度レベル「Ｅ」以上であっても、搬送波信号の品質を向上させることが可能である。 As a result, it is possible to further improve the quality of the carrier wave signal without preparing receivers with different reception performance for each transmission distance. Further, even if the intensity level "Em" of the electrical signal (frequency-modulated batch-converted signal) is initially at or above the intensity level "E", it is possible to improve the quality of the carrier wave signal.
　（第３実施形態）
　第３実施形態では、波長分散による光信号の波形歪が補償される点が、第２実施形態との差分である。第３実施形態では、第２実施形態との差分を中心に説明する。 (Third Embodiment)
The difference between the third embodiment and the second embodiment is that the waveform distortion of the optical signal due to chromatic dispersion is compensated. 3rd Embodiment demonstrates centering around the difference with 2nd Embodiment.
　図６は、第３実施形態における、受信装置５ｃの構成例を示す図である。受信装置５ｃは、図１に示された受信装置５に対応する。受信装置５ｃは、物理量測定部５１ｃと、制御部５２ｃと、レベル増幅部５３ｃと、光学処理部５４ｃと、復調部５５と、搬送波信号増幅部５６ｂと、補償部５７とを備える。 FIG. 6 is a diagram showing a configuration example of the receiving device 5c in the third embodiment. The receiving device 5c corresponds to the receiving device 5 shown in FIG. The receiving device 5c includes a physical quantity measuring section 51c, a control section 52c, a level amplifying section 53c, an optical processing section 54c, a demodulating section 55, a carrier wave signal amplifying section 56b, and a compensating section 57.
　制御部５２ｃと、レベル増幅部５３ｃと、光学処理部５４ｃとは、図４に示された制御部５２ｂと、レベル増幅部５３ｂと、光学処理部５４ｂとに対応する。光学処理部５４ｃは、変換部５４０と、プリアンプ５４２とを備える。搬送波信号増幅部５６ｃは、濾波器５６０と、ポストアンプ５６１と、分岐部５６２とを備える。 The control unit 52c, the level amplification unit 53c, and the optical processing unit 54c correspond to the control unit 52b, the level amplification unit 53b, and the optical processing unit 54b shown in FIG. The optical processing section 54 c includes a conversion section 540 and a preamplifier 542 . The carrier wave signal amplifying section 56 c includes a filter 560 , a post-amplifier 561 and a branching section 562 .
　搬送波信号増幅部５６ｃは、分岐部５６２の前段及び後段の少なくとも一方に、電気アンプを更に備えてもよい。これによって、分岐部５６２による電気信号の分岐に伴って電気信号の強度レベルが低下した場合でも、電気信号の強度レベルを補償することができる。 The carrier wave signal amplification section 56c may further include an electric amplifier in at least one of the front stage and the rear stage of the branch section 562. As a result, even if the intensity level of the electrical signal is lowered due to branching of the electrical signal by the branching unit 562, the intensity level of the electrical signal can be compensated.
　補償部５７には、光信号が分岐装置４から入力される。補償部５７は、補償量を表す制御信号を、制御部５２ｃから取得する。補償部５７は、制御信号を用いて制御部５２ｃから指示された補償量に基づいて、波長分散による光信号の波形歪を補償する。補償部５７は、波形歪が補償された光信号を、レベル増幅部５３ｃに出力する。 An optical signal is input from the branching device 4 to the compensation unit 57 . The compensation unit 57 acquires a control signal representing the amount of compensation from the control unit 52c. The compensator 57 compensates for waveform distortion of the optical signal due to chromatic dispersion based on the amount of compensation instructed by the controller 52c using the control signal. The compensator 57 outputs the optical signal whose waveform distortion has been compensated for to the level amplifier 53c.
　制御部５２ｃは、変換部５４０が受光可能な光信号の強度レベルの範囲「Ｐｄ～Ｐｕ」［ｄＢｍ］を表すデータと、映像再生に必要とされる電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」を表すデータとを、予め保持している。 The control unit 52c controls data representing the range “Pd to Pu” [dBm] of the intensity level of the optical signal that can be received by the conversion unit 540, and the carrier-to-noise ratio “CNR(i )” is stored in advance.
　制御部５２ｃは、電気信号の強度レベル「Ｅｍ」が強度レベル「Ｅ」以上となり、かつ、変換部５４０に入力される光信号の強度レベルが下限「Ｐｄ」から上限「Ｐｕ」までの範囲に収まるように、レベル増幅部５３ｃにおける光信号の増幅ゲインを調整する。制御部５２ｃは、増幅ゲインを表す制御信号を、レベル増幅部５３ｃに出力する。 The control unit 52c controls the intensity level “Em” of the electric signal to be equal to or higher than the intensity level “E” and the intensity level of the optical signal input to the conversion unit 540 to be within the range from the lower limit “Pd” to the upper limit “Pu”. The amplification gain of the optical signal in the level amplification unit 53c is adjusted so as to be contained. The controller 52c outputs a control signal representing the amplification gain to the level amplifier 53c.
　制御部５２ｃは、電気信号（映像信号）の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が小さいか否かを判定する。制御部５２ｃは、電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が小さい場合、現在の補償量よりも一定幅「Ｖｗ」だけ多い補償量で光信号の波形を補償部５７が補償するように、補償部５７における光信号の波形歪の補償量を調整する。 The control unit 52c determines whether the carrier-to-noise ratio "CNRm(i)" of the electrical signal is smaller than the carrier-to-noise ratio "CNR(i)" of the electrical signal (video signal). When the carrier-to-noise ratio "CNRm(i)" of the electrical signal is smaller than the carrier-to-noise ratio "CNR(i)" of the electrical signal, the control unit 52c increases the current compensation amount by a certain width "Vw". The amount of compensation for the waveform distortion of the optical signal in the compensator 57 is adjusted so that the compensator 57 compensates for the waveform of the optical signal with the amount of compensation.
　制御部５２ｃは、電気信号（映像信号）の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が小さいか否かを再度判定する。制御部５２ｃは、必要とされる電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」よりも電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が小さい場合、補償部５７における光信号の波形歪の補償量を再調整する。制御部５２ｃは、レベル増幅部５３ｃにおける光信号の増幅ゲインを再調整してもよい。 The control unit 52c determines again whether the carrier-to-noise ratio "CNRm(i)" of the electrical signal (video signal) is smaller than the carrier-to-noise ratio "CNR(i)" of the electrical signal (video signal). When the carrier-to-noise ratio "CNRm(i)" of the electrical signal is smaller than the required carrier-to-noise ratio "CNR(i)" of the electrical signal, the controller 52c controls the waveform distortion of the optical signal in the compensator 57. Readjust the amount of compensation for The controller 52c may readjust the amplification gain of the optical signal in the level amplifier 53c.
　制御部５２ｃは、電気信号の搬送波対雑音比「ＣＮＲｍ（ｉ）」が電気信号の搬送波対雑音比「ＣＮＲ（ｉ）」以上であると判定されるまで、補償部５７における光信号の波形歪の補償量を再調整する。制御部５２ｃは、レベル増幅部５３ｃにおける光信号の増幅ゲインを再調整してもよい。ただし、波形歪の補償量が補償量の上限を上回る場合には、制御部５２ｃは、波形歪の補償量が補償量の上限を上回らないように、補償量の再調整処理を中止する。 The controller 52c controls the waveform distortion of the optical signal in the compensator 57 until it is determined that the carrier-to-noise ratio "CNRm(i)" of the electrical signal is greater than or equal to the carrier-to-noise ratio "CNR(i)" of the electrical signal. Readjust the amount of compensation for The controller 52c may readjust the amplification gain of the optical signal in the level amplifier 53c. However, if the waveform distortion compensation amount exceeds the upper limit of the compensation amount, the control unit 52c stops the compensation amount readjustment process so that the waveform distortion compensation amount does not exceed the upper limit of the compensation amount.
　制御部５２ｃが実行する制御のアルゴリズムは、特定のアルゴリズムに限定されない。制御部５２ｂは、例えば二分探索法又は非線形最小二乗法等の最適化手法を用いて、補償量の調整処理を実行する。 The control algorithm executed by the control unit 52c is not limited to a specific algorithm. The control unit 52b executes compensation amount adjustment processing using, for example, an optimization method such as a binary search method or a nonlinear least-squares method.
　次に、光伝送システム１の動作例を説明する。
　図７は、第３実施形態における、光伝送システム１の動作例を示すフローチャートである。光伝送システム１は、図７にフローチャートを用いて示された動作を、所定周期で実行する。 Next, an operation example of the optical transmission system 1 will be described.
FIG. 7 is a flow chart showing an operation example of the optical transmission system 1 in the third embodiment. The optical transmission system 1 performs the operation shown using the flowchart in FIG. 7 at predetermined intervals.
　補償部５７は、制御信号を用いて制御部５２ｃから指示された補償量に基づいて、波長分散による光信号の波形歪を補償する（ステップＳ３０１）。ステップＳ３０２からステップＳ３０５までの動作は、図５に示されたステップＳ２０２からステップＳ２０５までの動作と同様である。 The compensation unit 57 compensates for waveform distortion of the optical signal due to chromatic dispersion based on the amount of compensation instructed by the control unit 52c using the control signal (step S301). The operations from step S302 to step S305 are the same as the operations from step S202 to step S205 shown in FIG.
　搬送波雑音比が搬送波信号の閾値未満（品質基準未満）であると判定された場合（ステップＳ３０５：ＮＯ）、制御部５２ｃは、補償部５７が光信号の波形歪の補償量を一定幅「Ｖｗ」だけ更に増加させるように、制御信号を生成する。補償部５７は、光信号の波形歪の補償量を一定幅「Ｖｗ」だけ更に増加させる（ステップＳ３０６）。 If it is determined that the carrier-to-noise ratio is less than the threshold value of the carrier signal (less than the quality standard) (step S305: NO), the controller 52c causes the compensator 57 to set the amount of compensation for the waveform distortion of the optical signal to the constant width "Vw ” to further increase the control signal. The compensation unit 57 further increases the amount of compensation for the waveform distortion of the optical signal by the constant width "Vw" (step S306).
　制御部５２ｃは、一定幅「Ｖｗ」だけ更に増加された補償量が上限を上回るか否かを判定する（ステップＳ３０７）。一定幅「Ｖｗ」だけ更に増加された補償量が上限以下であると判定された場合（ステップＳ３０７：ＮＯ）、光伝送システム１は、図７にフローチャートを用いて示された動作を終了する。一定幅「Ｖｗ」だけ更に増加された補償量が上限を上回ると判定された場合（ステップＳ３０７：ＹＥＳ）、制御部５２ｃは、補償部５７が光信号の波形歪の補償量を一定幅だけ更に増加させる処理を中止するように、制御信号を生成する。補償部５７は、光信号の波形歪を上限の補償量で補償する（ステップＳ３０８）。 The control unit 52c determines whether or not the compensation amount further increased by the constant width "Vw" exceeds the upper limit (step S307). If it is determined that the amount of compensation further increased by the constant width "Vw" is equal to or less than the upper limit (step S307: NO), the optical transmission system 1 terminates the operation shown using the flowchart in FIG. If it is determined that the compensation amount further increased by the constant width "Vw" exceeds the upper limit (step S307: YES), the control unit 52c causes the compensation unit 57 to further increase the compensation amount for the waveform distortion of the optical signal by the constant width. A control signal is generated to stop the increasing process. The compensation unit 57 compensates for the waveform distortion of the optical signal with the upper limit compensation amount (step S308).
　以上のように、補償部５７は、受信された光信号の波形歪を補償する。変換部５４０は、受信された光信号を電気信号に変換する。復調部５５は、電気信号に基づいて搬送波信号を生成する。物理量測定部５１ｃは、搬送波信号の物理量を測定する。例えば、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とのうちの少なくとも一つである。制御部５２ｃは、搬送波信号の物理量が第２閾値未満（品質基準未満）である場合、受信された光信号の物理量を調整する。例えば、制御部５２ｃは、搬送波信号の物理量が第２閾値未満である場合、受信された光信号の波形歪の補償量を増加させる。 As described above, the compensator 57 compensates for waveform distortion of the received optical signal. The converter 540 converts the received optical signal into an electrical signal. A demodulator 55 generates a carrier wave signal based on the electrical signal. The physical quantity measuring unit 51c measures the physical quantity of the carrier signal. For example, at least one of the carrier-to-noise ratio, the amount of composite second order distortion, and the amount of composite third order distortion. The controller 52c adjusts the physical quantity of the received optical signal when the physical quantity of the carrier signal is less than the second threshold (less than the quality standard). For example, when the physical quantity of the carrier signal is less than the second threshold, the controller 52c increases the amount of compensation for waveform distortion of the received optical signal.
　これによって、伝送距離ごとに異なる受信性能の受信装置が用意されなくても、搬送波信号の品質を向上させることが可能である。入力された光信号の波形が波長分散によって劣化している場合でも、搬送波信号の品質を向上させることが可能である。 As a result, it is possible to improve the quality of carrier signals without preparing receivers with different reception performance for different transmission distances. Even if the waveform of the input optical signal is degraded by chromatic dispersion, it is possible to improve the quality of the carrier signal.
　第３実施形態では、受信装置５ｃは、入力された光信号の波形歪を補償することによって、出力される搬送波信号の品質を改善する。これによって、中継装置３－ｎと受信装置５ｃとの間の伝送距離を長くすることができるので、より広いエリアにおいて同じ受信性能の受信装置５ｃを使用することが可能である。 In the third embodiment, the receiving device 5c improves the quality of the output carrier signal by compensating for the waveform distortion of the input optical signal. As a result, the transmission distance between the relay device 3-n and the receiving device 5c can be lengthened, so that the receiving device 5c with the same reception performance can be used in a wider area.
　光信号の波長分散による波形歪を送信装置２（基地局側）が補償しなくてもよいので、受信装置５（アクセス用の光アンプのポート）とユーザ端末（不図示）との間のアクセス距離がばらついていても、搬送波信号の品質を向上させることが可能である。すなわち、光信号の波長分散による波形歪を受信装置５が補償するので、受信装置５とユーザ端末（不図示）との間のアクセス距離がばらついている場合でも、搬送波信号の品質を向上させることが可能である。 Since the transmitter 2 (base station side) does not have to compensate for the waveform distortion due to the chromatic dispersion of the optical signal, the access between the receiver 5 (port of the optical amplifier for access) and the user terminal (not shown) Even if the distance varies, it is possible to improve the quality of the carrier signal. That is, since the receiving device 5 compensates for the waveform distortion caused by the chromatic dispersion of the optical signal, the quality of the carrier wave signal can be improved even when the access distance between the receiving device 5 and the user terminal (not shown) varies. is possible.
　（ハードウェア構成例）
　図８は、各実施形態における、受信装置５のハードウェア構成例を示す図である。受信装置５の各機能部のうちの一部又は全部は、ＣＰＵ（Central Processing Unit）等のプロセッサ１００が、不揮発性の記録媒体（非一時的な記録媒体）を有する記憶装置１０２とメモリ１０１とに記憶されたプログラムを実行することにより、ソフトウェアとして実現される。プログラムは、コンピュータ読み取り可能な記録媒体に記録されてもよい。コンピュータ読み取り可能な記録媒体とは、例えばフレキシブルディスク、光磁気ディスク、ＲＯＭ（Read Only Memory）、ＣＤ－ＲＯＭ（Compact Disc Read Only Memory）等の可搬媒体、コンピュータシステムに内蔵されるハードディスク等の記憶装置などの非一時的な記録媒体である。 (Hardware configuration example)
FIG. 8 is a diagram showing a hardware configuration example of the receiving device 5 in each embodiment. Some or all of the functional units of the receiving device 5 are a processor 100 such as a CPU (Central Processing Unit) and a storage device 102 having a non-volatile recording medium (non-temporary recording medium) and a memory 101. It is implemented as software by executing a program stored in the . The program may be recorded on a computer-readable recording medium. Computer-readable recording media include portable media such as flexible discs, magneto-optical discs, ROM (Read Only Memory), CD-ROM (Compact Disc Read Only Memory), and storage such as hard disks built into computer systems. It is a non-temporary recording medium such as a device.
　受信装置５の各機能部の一部又は全部は、例えば、ＬＳＩ（Large Scale Integrated circuit）、ＡＳＩＣ（Application Specific Integrated Circuit）、ＰＬＤ（Programmable Logic Device）又はＦＰＧＡ（Field Programmable Gate Array）等を用いた電子回路（electronic circuit又はcircuitry）を含むハードウェアを用いて実現されてもよい。 Some or all of the functional units of the receiving device 5 are, for example, LSI (Large Scale Integrated circuit), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), FPGA (Field Programmable Gate Array), etc. It may be implemented using hardware including electronic circuits or circuitry.
　上記の各実施形態は、互いに組み合わされてもよい。 Each of the above embodiments may be combined with each other.
　以上、この発明の実施形態について図面を参照して詳述してきたが、具体的な構成はこの実施形態に限られるものではなく、この発明の要旨を逸脱しない範囲の設計等も含まれる。 Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design within the scope of the gist of the present invention.
　本発明は、光信号を用いて映像信号等を伝送する光伝送システムに適用可能である。 The present invention is applicable to optical transmission systems that transmit video signals and the like using optical signals.
１…光伝送システム、２…送信装置、３…中継装置、４…分岐装置、５，５ａ，５ｂ，５ｃ…受信装置、５０…レベル測定部、５１ａ，５１ｂ…物理量測定部、５２ｃ…制御部、５３ａ，５３ｃ…レベル増幅部、５４ａ，５４ｂ…光学処理部、５５…復調部、５６ａ，５６ｂ…搬送波信号増幅部、５７…補償部、１００…プロセッサ、１０１…メモリ、１０２…記憶装置、５４０…変換部、５４１…分岐部、５４２…プリアンプ、５６０…濾波器、５６１…ポストアンプ、５６２…分岐部 DESCRIPTION OF SYMBOLS 1... Optical transmission system 2... Transmission apparatus 3... Repeater 4... Branching apparatus 5, 5a, 5b, 5c... Receiving apparatus 50... Level measuring part 51a, 51b... Physical quantity measuring part 52c... Control part , 53a, 53c... Level amplifier 54a, 54b... Optical processor 55... Demodulator 56a, 56b... Carrier wave signal amplifier 57... Compensator 100... Processor 101... Memory 102... Storage device 540 Conversion unit 541 Branch unit 542 Preamplifier 560 Filter 561 Post amplifier 562 Branch unit

Claims (8)

  1. 　受信された光信号を電気信号に変換する変換部と、
    　前記電気信号に基づいて搬送波信号を生成する復調部と、
    　前記電気信号の物理量又は前記搬送波信号の物理量を測定する物理量測定部と、
    　前記電気信号の物理量が第１閾値未満である場合、又は、前記搬送波信号の物理量が第２閾値未満である場合、前記受信された光信号の物理量を調整する制御部と
    　を備える受信装置。     a converter that converts the received optical signal into an electrical signal;
    a demodulator that generates a carrier wave signal based on the electrical signal;
    a physical quantity measuring unit that measures the physical quantity of the electrical signal or the physical quantity of the carrier signal;
    a control unit that adjusts the physical quantity of the received optical signal when the physical quantity of the electrical signal is less than a first threshold or when the physical quantity of the carrier signal is less than a second threshold.
  2. 　前記電気信号の物理量は、前記受信された光信号の強度レベルであり、
    　前記制御部は、前記電気信号の物理量が前記第１閾値未満である場合、前記受信された光信号の強度レベルを増幅させる、
    　請求項１に記載の受信装置。     the physical quantity of the electrical signal is the intensity level of the received optical signal;
    The controller amplifies the intensity level of the received optical signal when the physical quantity of the electrical signal is less than the first threshold.
    The receiving device according to claim 1.
  3. 　前記搬送波信号の物理量は、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とのうちの少なくとも一つであり、
    　前記制御部は、前記搬送波信号の物理量が前記第２閾値未満である場合、前記受信された光信号の強度レベルを増幅させる、
    　請求項１に記載の受信装置。     the physical quantity of the carrier signal is at least one of a carrier-to-noise ratio, a composite second-order distortion amount, and a composite third-order distortion amount;
    The controller amplifies the intensity level of the received optical signal when the physical quantity of the carrier signal is less than the second threshold.
    The receiving device according to claim 1.
  4. 　前記受信された光信号の波形歪を補償する補償部を備え、
    　前記搬送波信号の物理量は、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とのうちの少なくとも一つであり、
    　前記制御部は、前記搬送波信号の物理量が前記第２閾値未満である場合、前記受信された光信号の波形歪の補償量を増加させる、
    　請求項１に記載の受信装置。     a compensator for compensating for waveform distortion of the received optical signal;
    the physical quantity of the carrier signal is at least one of a carrier-to-noise ratio, a composite second-order distortion amount, and a composite third-order distortion amount;
    When the physical quantity of the carrier signal is less than the second threshold, the control unit increases a compensation amount for waveform distortion of the received optical signal.
    The receiving device according to claim 1.
  5. 　受信装置が実行する受信方法であって、
    　受信された光信号を電気信号に変換する変換ステップと、
    　前記電気信号に基づいて搬送波信号を生成する復調ステップと、
    　前記電気信号の物理量又は前記搬送波信号の物理量を測定する物理量測定ステップと、
    　前記電気信号の物理量が第１閾値未満である場合、又は、前記搬送波信号の物理量が第２閾値未満である場合、前記受信された光信号の物理量を調整する制御ステップと
    　を含む受信方法。     A receiving method executed by a receiving device,
    a converting step of converting the received optical signal into an electrical signal;
    a demodulating step of generating a carrier signal based on said electrical signal;
    a physical quantity measuring step of measuring the physical quantity of the electrical signal or the physical quantity of the carrier wave signal;
    and a control step of adjusting the physical quantity of the received optical signal when the physical quantity of the electrical signal is less than a first threshold or when the physical quantity of the carrier signal is less than a second threshold.
  6. 　前記電気信号の物理量は、前記受信された光信号の強度レベルであり、
    　前記制御ステップでは、前記電気信号の物理量が前記第１閾値未満である場合、前記受信された光信号の強度レベルを増幅させる、
    　請求項５に記載の受信方法。     the physical quantity of the electrical signal is the intensity level of the received optical signal;
    In the control step, if the physical quantity of the electrical signal is less than the first threshold, the intensity level of the received optical signal is amplified.
    The receiving method according to claim 5.
  7. 　前記受信された光信号の波形歪を補償する補償ステップを含み、
    　前記搬送波信号の物理量は、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とのうちの少なくとも一つであり、
    　前記制御ステップでは、前記搬送波信号の物理量が前記第２閾値未満である場合、前記受信された光信号の強度レベルを増幅させる、
    　請求項５に記載の受信方法。     comprising a compensating step of compensating for waveform distortion of the received optical signal;
    the physical quantity of the carrier signal is at least one of a carrier-to-noise ratio, a composite second-order distortion amount, and a composite third-order distortion amount;
    The control step amplifies the intensity level of the received optical signal if the physical quantity of the carrier signal is less than the second threshold.
    The receiving method according to claim 5.
  8. 　前記搬送波信号の物理量は、搬送波対雑音比と、複合２次歪の量と、複合３次歪の量とのうちの少なくとも一つであり、
    　前記制御ステップでは、前記搬送波信号の物理量が前記第２閾値未満である場合、前記受信された光信号の波形歪の補償量を増加させる、
    　請求項５に記載の受信方法。     the physical quantity of the carrier signal is at least one of a carrier-to-noise ratio, a composite second-order distortion amount, and a composite third-order distortion amount;
    In the control step, if the physical quantity of the carrier signal is less than the second threshold, increasing the amount of compensation for waveform distortion of the received optical signal.
    The receiving method according to claim 5.
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JP2003152646A (en) * 2001-11-15 2003-05-23 Matsushita Electric Ind Co Ltd Variable wavelength distribution compensation system for analog optical transmission
JP2010093719A (en) * 2008-10-10 2010-04-22 Nec Commun Syst Ltd Optical signal receiver, optical transmission apparatus, and method of detecting abnormal condition in optical signal

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