JP2010226669A - Optical signal transmission system and optical receiver for optical signal transmission system - Google Patents

Abstract

An object of the present invention is to select and output an electrical signal corresponding to an input optical signal that is determined to be effective when redundancy is made, and to allow a reduction in light intensity to the lower limit of reception.
An optical transmitter having an electrical / optical converter that converts a plurality of serial digital data signals into a plurality of optical signals having wavelengths suitable for optical wavelength multiplexing, and wavelength-multiplexing the plurality of converted optical signals. An optical wavelength multiplexing device that outputs as a multiplexed optical signal, an optical wavelength separation device that separates the multiplexed optical signal into a plurality of optical signals, and an optical / electrical converter that converts the plurality of separated optical signals into electrical signals In a system composed of optical receivers, the optical receiver includes two or more optical signal input units, and inputs such as light intensity or modulation components and amplitudes of electric signals after optical / electrical conversion of the two or more input optical signals. The optical signal information is detected, the validity of the input optical signal is determined based on the detected input optical signal information, and the electrical signal corresponding to the input optical signal determined to be valid is switched and output. .
[Selection] Figure 2

Description

  The present invention relates to an optical signal transmission system capable of optical wavelength multiplexing transmission of various serial digital signals used for transmission of broadcasting materials and data, and an optical receiver for the optical signal transmission system used therefor. It can be used for transmission of broadcasting material to a center (including a station such as a cable TV) and the like and transmission of broadcasting material between a plurality of broadcasting centers.

Corresponding to the recent digital broadcasting, higher definition of broadcasting materials is progressing, and an optical signal transmission system via an optical fiber cable has been introduced in part.
In order to efficiently transmit a plurality of broadcasting materials, an HD-SDI (High Definition Serial Digital Interface) signal, an SD-SDI (Standard Definition Serial Digital Interface) signal, and a DVB-ASI (Digital Video Broadcasting. Asynchronous Serial Interface) signal In some cases, an optical wavelength division multiplex transmission system has been introduced in which various serial digital signals such as and the like can be transmitted with fewer optical fiber cables than the number of signals.
The broadcast material transmission method using optical fiber cable enables long-distance transmission, and the optical wavelength multiplexing transmission system can increase the number of broadcast material transmission per fiber cable, while the optical fiber is broken or the equipment in the route is broken. The necessity of backup (redundancy of equipment and optical transmission path) against the above disconnection and failure, mainly in the case of transmitting live broadcasts and important broadcast materials, to include risks such as transmission stoppage or temporary suspension of transmission Is growing.

One conventional optical signal transmission system having a backup function is shown in FIG. This optical signal transmission system multiplexes a large number of optical signals having different wavelengths transmitted from a plurality of optical transmission devices TX (λ ₁ ) to TX (λ _n ) by an optical wavelength multiplexing device WDM, and optical wavelength multiplexing device WDM The multiplexed optical signal output from the optical signal is branched by an optical branching device (coupler) C and transmitted through a plurality of optical transmission lines L. A plurality of optical input units and a single optical output unit are provided in front of the optical wavelength demultiplexing device WDM. The optical signal switching device OSW having the optical signal input from the plurality of optical transmission lines L to the optical signal switching device OSW is compared with a preset switching threshold value, and the optical signal switching device OSW If it is determined that the input is not valid, and if it is determined that the input is valid, the optical signal switching device OSW determines the optical input unit and the optical signal corresponding to the optical signal according to information such as the priority order of the preset route. The output is switched to ensure the output path and light The data is sent to the receiving unit RX.

Another example of a conventional optical transmission system is shown in FIG. In this optical transmission system, a plurality of optical transmission device groups TX1 (TX (λ ₁ ) to TX (λ _n )) and TX2 (TX (λ ₁ ) to share a signal source that can be operated in the same or alternative manner for each wavelength. TX (λ _n )),..., TXn, and a plurality of optical signals λ _{1 to} λ _n having different wavelengths output from the optical transmission device groups TX 1, TX 2,. A plurality of combinations of optical wavelength multiplexers WDM1, WDM2,..., WDMn that output as wavelength multiplexed optical signals are arranged, and output from each set of optical wavelength multiplexers WDM1, WDM2,. The multiplexed optical signal is transmitted using a plurality of optical transmission lines L, an optical signal switching device OSW having a plurality of optical input units and one optical output unit is disposed in front of the optical wavelength demultiplexing device WDM, From each of the optical transmission lines L, an optical signal switching device O The light intensity of the optical signal input to W is compared with a preset switching threshold, and if it is equal to or lower than the threshold, it is determined that the optical input is not effective, and if it is determined effective, the optical signal switching device The OSW is switched so as to secure a path between the optical input unit and the optical output unit corresponding to the optical signal in accordance with information such as a preset path priority order, and is sent to the optical receiving unit RX. It is.

In the optical transmission systems of FIGS. 13 and 14, a plurality of optical signals λ _{1 to} λ _n having different wavelengths are propagated through the optical transmission line. When a plurality of optical signals λ _{1 to} λ _n having different wavelengths propagate through a single optical fiber, the optical intensity of the multiplexed optical signal is the total optical power of the optical signals of the respective wavelengths. The optical signal switching device OSW shown in FIGS. 13 and 14 compares the light intensity of each optical signal input to each optical input unit with a preset switching threshold value. When the optical signal switching unit OSW is below the threshold value, the optical input unit is effective. Therefore, the threshold value needs to be set based on the total optical power of each optical input unit of the optical signal switching device OSW. In this case, there are the following problems.

  1. Since the intensity of the optical signal of each wavelength is not uniform in the multiplexed optical signal, there is a restriction on the system construction that the switching threshold must be set based on the optical signal of the wavelength having the smallest optical intensity.

2. Since the total optical power of the multiplexed optical signal is obtained as a sum of the average values of the optical intensities of the optical signals of the respective wavelengths, light that is smaller than the signal light of other wavelengths, such as the optical signal wavelength λ ₂ shown in FIG. In the optical signal having the intensity, the light intensity after passing through the optical wavelength separation device WDM in FIG. 14 is relatively smaller than the light intensity of other wavelengths. In order to maintain the optical intensity of the optical input unit of the optical receiver RX of FIG. 14 that receives the optical signal corresponding to the optical signal wavelength λ ₂ higher than the optical intensity that is the reception lower limit, the optical signal switching apparatus OSW for switching is used. Since the threshold must be set lower than necessary (for optical signals of other wavelengths), the path is switched before the light reception lower limit is reached in the optical receiver to which optical signals of other wavelengths are input. (The range of the light intensity that can be operated becomes narrow), and the performance of the optical receiver cannot be fully utilized, which is a problem in system design.

3. In FIG. 14, when the number of optical transmitters TX is increased after the start of operation, or the number of optical transmitters TX is not changed, it is in a non-operational state (power supply OFF or optical fiber not connected) at the start of operation. When the operation of the optical transmitter TX is started from a certain time, the total optical power of the multiplexed optical signal increases at that time. Since the threshold value for switching is compared with the total optical power, the optical intensity of the threshold value converted per optical signal decreases as the number of optical wavelengths increases (example in the initial state: FIG. 16, example after the increase in total optical power) : FIG. 17). That is, in the case of λ ₂ , if the total optical power of one optical input unit of the optical signal switching device is set to switch to the path of the other optical input unit when Δa decreases, the path does not decrease Δb. May not be switched (for example, the path may not be switched even if the light reception lower limit of the optical receiver is not met), there is a possibility that operation on the system may be hindered.

  4). If the number of optical transmitters TX decreases after the start of operation, or the number of optical transmitters TX is not changed, it is operated at the beginning of operation, and the operation is suspended or suspended from a certain time (power off or optical fiber not yet used). In the case of connection), the total optical power decreases at that time. Since the threshold value for switching is compared with the total optical power, the light intensity of the threshold value converted per optical signal increases as the number of optical wavelengths decreases (example in the initial state: FIG. 18, example after the total optical power is reduced) : FIG. 19). That is, even in the case of n-wave transmission as in the initial state, even if the threshold light intensity converted per optical signal is set lower than the optical signal intensity of each wavelength, one optical signal can be obtained by reducing the number of wavelengths. The light intensity of the threshold value converted in the vicinity increases and becomes larger than the light intensity of a part or all of the optical signals, and the light intensity after passing through the optical wavelength demultiplexer WDM (FIGS. 13 and 14) is received by the optical receiver RX. Even if there is a sufficient margin with respect to the allowable lower limit, there is a possibility that the operation on the system may be hindered, for example, the optical path may be switched.

  5. Since the optical signal switching device (OSW: FIG. 13 and FIG. 14) switches the path through which the multiplexed signal light passes, if switching occurs, all signal light is routed to another path even if some signal light is normal. Switch. In this case, a problem occurs when normal signal light is desired to be operated in the route that has been transmitted until then. Further, when switching occurs, even in normal signal light, an instantaneous interruption of the optical signal occurs, which causes a temporary interruption of broadcasting material transmission, which is a problem in system operation.

  6). Since the optical signal switching device OSW (FIGS. 13 and 14) employs a method of switching the path according to the total optical power of the multiplexed optical signal input to each optical input unit, the modulation component of each signal light satisfies the transmission performance. There is no means to judge whether or not. That is, even if the intensity of the optical signal of each signal is sufficient, the modulation signal component may not satisfy the transmission performance, but the optical signal switching device OSW cannot determine this, There is a possibility that the transmission of the actual modulation signal may be hindered.

The optical signal transmission system for serial digital signals according to the present invention, as described in claim 1 (for example, FIG. 1), converts the plurality of serial digital data signals into a plurality of optical signals having wavelengths suitable for optical wavelength multiplexing. An optical transmitter TX having an optical converter, an optical wavelength multiplexer WDM for wavelength-multiplexing a plurality of optical signals λ _{1 to} λ _n converted by the optical transmitter TX, and outputting the multiplexed optical signal; An optical wavelength separation device WDM that separates an optical signal into a plurality of optical signals, an optical transmission path through which the multiplexed optical signal propagates, and light that converts a plurality of optical signals separated by the optical wavelength separation device WDM into electrical signals / An optical signal transmission system including an optical receiver RX having an electrical conversion unit, and the optical receiver RX includes two or more optical signal input units 1 as shown in FIGS. 5 to 8, for example. Part 1 The optical / electrical conversion unit (PD) 2 performs optical / electrical conversion on the two or more optical signals that are applied, and based on the converted electric signal, the intensity, modulation component, amplitude, The detection unit 3 detects all or part of the input optical signal information such as timing accuracy, signal transmission speed, reclocking state, and error rate, and the control unit 5 determines the effectiveness of the input optical signal based on the detected input optical signal information. The switch 4 selects and outputs an electrical signal corresponding to the input optical signal determined to be effective.

  According to the optical signal transmission system of the present invention, as described in claim 2 (for example, FIGS. 5 to 8), on the output side of the switch 4, a clock with little temporal fluctuation is obtained from information included in the electrical signal. Generate and reshape the waveform of the electric signal based on this, and the electric signal can be taken in and re-output so as to satisfy the required amplitude when the electric signal is output to the outside of the optical receiver for the optical signal transmission system It can also be done.

  According to the optical signal transmission system of the present invention, as in claim 3 (for example, FIG. 10), the optical transmission device TX and the optical wavelength multiplexing device WDM are arranged in the transmission station 20, and the optical reception device RX and the optical wavelength demultiplexing device. The device WDM may be arranged in the receiving station 21 so that optical signal transmission is possible between the transmitting station 20 and the receiving station 21.

  The optical signal transmission system according to the present invention, as described in claim 4 (for example, FIG. 10 to FIG. 12), is an optical signal input to two or more optical signal input units 1 of the optical receiver RX, Redundant optical transmission line TX for transmitting optical signal transmission apparatus TX, one or more of optical wavelength multiplexing apparatus WDM and optical wavelength demultiplexing apparatus WDM arranged in the optical signal path, and / or multiplexed optical signal can do. In this case, as described in claim 5 (for example, FIG. 12), the optical signal transmitted from the optical transmitter TX is transmitted in the same direction (for example, clockwise) or in the opposite direction (for example, counterclockwise) on the redundant optical transmission line. ) Can be transmitted.

  The optical signal transmission system according to the present invention is preset when an optical signal corresponding to an input optical signal determined to be valid is selected from two or more electric signals in the optical receiver RX. In addition to the preset priority of the input unit, if the currently selected input unit is valid, the selection may be made according to the priority of the input unit. The state can also be maintained.

  The optical receiver for an optical signal transmission system according to the present invention is input to two or more optical signal input units 1 and the respective optical signal input units 1 as described in claim 8 (for example, FIGS. 5 to 8). An optical / electrical converter (for example, PD) 2 that performs O / E conversion of the optical signal, and the intensity, modulation component, amplitude, timing accuracy, and signal transmission of each of the two or more input optical signals based on the converted electrical signal A detection unit 3 that detects all or part of optical signal information such as speed, reclocking state, and error rate; a switch 4 that switches and outputs an electrical signal converted by the optical / electrical conversion unit 2; and the optical / electrical conversion. Of the two or more electrical signals converted by the unit 2, the validity of each input optical signal is determined based on the optical signal information detected by the detection unit 3, and the electrical corresponding to the input optical signal determined to be valid Select a signal and output its electrical signal A control unit 5 for controlling the switching of the sea urchin the switching device 4, is provided with electrothermal output section 6 electrical signal passed through the switch 4 is output.

  The optical receiver for an optical transmission system according to the present invention has little temporal fluctuation from the information included in the electrical signal on the output side of the switch 4 as described in claim 9 (for example, FIGS. 5 to 8). An electric signal reclocking unit 7 that generates a clock and reshapes the waveform of the electric signal based on the clock, and an electric signal that is re-output using means of electric signal amplitude so that the electric signal output to the outside satisfies a required amplitude. The signal drive unit 8 or the electric signal drive unit 8 is provided.

  The detection unit 3 in the optical receiver for an optical signal transmission system according to the present invention is configured such that the detection unit 3 is converted into the light intensity of the electrical signal converted by the optical / electrical conversion unit 2 as described in claim 10 (for example, FIG. 5). The control unit 5 selects an electrical signal corresponding to the optical signal determined to be valid based on the intensity detected by the light intensity detection unit, and outputs the electrical signal. The switch 4 can be switched and controlled. As in the eleventh aspect (for example, FIG. 6), a modulation component detection unit that detects the modulation component of the electrical signal converted by the optical / electrical conversion unit 2 may be used. When the modulation component detection unit is used, the control unit 5 determines the effectiveness of the modulation component based on the detected modulation component information to determine the effectiveness, and the electrical signal corresponding to the optical signal determined to be effective. The switch 4 can be controlled to be switched so that the electrical signal is output.

  The optical receiver for an optical signal transmission system according to the present invention is the reclocking unit that detects the reclocking state of the electrical signal converted by the optical / electrical converter 2 as described in claim 12 (for example, FIG. 7). The control unit 5 determines the validity of the reclocking state based on the reclocking state information obtained from the reclocking state detection unit, and selects the electrical signal corresponding to the optical signal determined to be valid. The switch 4 can be switched and controlled so that an electric signal is output.

  The optical receiver for an optical signal transmission system according to the present invention has a serial / parallel converter 10 for serial / parallel conversion of an electric signal converted by the optical / electric converter 2 as described in claim 13 (for example, FIG. 8). And a parallel / serial conversion unit 11 for parallel / serial conversion of the parallel / serial-converted parallel signal converted by the conversion unit 10, and the detection unit 3 is a parallel converted by the serial / parallel conversion unit 10. The error detection unit detects error information such as a signal bit error rate and a data error, and the control unit 5 determines the validity of the bit error based on the error occurrence state obtained from the error detection unit or information similar to the bit error rate. The switch 4 is turned off so as to select and output an electrical signal corresponding to the optical signal judged effective. It is possible to e control.

  According to the optical receiver for an optical signal transmission system of the present invention, when the control unit 5 selects an electrical signal corresponding to the input optical signal determined to be valid from the two or more electrical signals, as described in claim 14. Further, a function of selecting according to a preset priority of the input unit is also provided, and the current selection is performed in addition to the preset priority of the input unit as described in claim 15. If the input unit is valid, it may have a function of maintaining the state.

The optical signal transmission system of the present invention performs O / E conversion on each optical signal input to two or more optical signal input units 1 of an optical receiver (RX) when equipment redundancy or optical transmission path redundancy is achieved. The electrical signal corresponding to the input optical signal determined to be valid is selected and output from the electrical signals, and the optical receiver for the optical signal transmission system of the present invention is input to two or more optical signal input units 1 The detection unit 3 that determines the validity of the electrical signal obtained by O / E converting each optical signal, and the electrical signal corresponding to the input optical signal determined to be valid are selected and output, and the following effects are obtained. .
1. As shown in FIG. 9, the transmission system is capable of allowing a decrease in light intensity up to the reception lower limit in all the optical receivers. In the conventional method, as shown in FIG. 15, the path is switched using the total optical power that changes depending on the number of optical signals multiplexed in the optical wavelength, so that the various problems described in the column “Problems to be solved by the invention” are Wiped out.
2. Since the effectiveness of light intensity, modulation component, etc. is judged for each optical signal, it is not necessary to review the switching threshold even if the number of wavelengths increases or decreases, and maintenance work during transmission system design and operation is easy. . In the conventional method, it is necessary to review the switching threshold every time the total optical power changes as the number of wavelengths increases or decreases.
3. Since the path is switched for each optical signal, even in an optical wavelength multiplexing transmission system, when some optical signals become ineffective, other normal optical signals are not switched to another path. No signal interruption occurs, preventing operational problems. In the conventional method, the path through which the multiplexed signal light passes is switched. When switching occurs, all the optical signals are switched to another path even if some of the optical signals are normal, and normal optical signals are transmitted until then. When it was desired to use the route that had been used, troubles (such as signal interruptions) sometimes occurred.
4). When device redundancy or optical transmission line redundancy is achieved, it is determined whether or not the light intensity of each of the optical signals input to the two or more optical signal input units 1 of the optical receiver RX satisfies a threshold (effectiveness). In addition to the method (method 1), all or part of information such as the intensity, modulation component, amplitude, timing accuracy, transmission speed, reclocking state, error rate, etc. of the electric signal after O / E conversion satisfies the transmission performance. It is also possible to output an electrical signal corresponding to the optical signal determined to be effective by the method (method 2) for determining whether (effectiveness) or not (when the optical signal is not transmitted (standby state)), When a safe optical path is secured using method 1 and an optical signal is transmitted, an electrical signal to be output is obtained by additionally determining whether other transmission performance is satisfied using method 2 as necessary. Operation that ensures the quality of It is also possible to.
5). On the output side of the switch 4, a clock with little temporal fluctuation is generated from the information included in the electrical signal, and the waveform of the electrical signal is reshaped based on the generated clock, and the electrical signal is optically received for the optical transmission system. Since the electrical signal can be re-output using means such as an amplitude of the electric signal so as to satisfy the amplitude required for output to the outside of the apparatus, the amplitude of the output electric signal is ensured.

  The optical signal transmission system of the present invention supports input optical signals that are determined to be valid among electrical signals obtained by O / E conversion of the respective optical signals input to two or more optical signal input units 1 of the optical receiver RX. When selecting an electrical signal to be selected, it is possible to select according to a preset priority order of the input section. In addition to the preset priority order of the input section, if the currently selected input section is valid, Since the state can also be maintained, for example, when an electrical signal corresponding to a low-priority optical input unit is selected, the high-priority optical input unit changes from an ineffective state to an effective state. However, there is also an effect that it can be operated so that the signal is not momentarily interrupted without automatically switching.

1 is a block diagram showing the basics of an optical wavelength multiplexing optical signal transmission system that is the basis of the present invention. The block diagram which shows an example of the redundancy by an optical wavelength multiplexing system which is an example of the optical signal transmission system of this invention. The block diagram of the redundancy example which is an example of the optical signal transmission system of this invention, is an optical wavelength multiplexing system, and the transmission side was provided with two or more transmission groups. Explanatory drawing which shows the redundant example of the optical signal transmission system which is not optical wavelength multiplexing. 1 is a block diagram illustrating an example of a light intensity detection method, which is an optical receiver for an optical signal transmission system according to the present invention. 1 is a block diagram illustrating an example of an optical modulation detection method, which is an optical receiver for an optical signal transmission system according to the present invention. 1 is a block diagram illustrating an example of an electrical signal reclocking detection system, which is an optical receiver for an optical signal transmission system according to the present invention. 1 is a block diagram illustrating an example of an electrical signal error detection method, which is an optical receiver for an optical signal transmission system according to the present invention. The light intensity comparison explanatory drawing in the optical signal transmission system of this invention. The block diagram which shows an example of the redundant system which is an optical signal transmission system of this invention, Comprising: Optical transmission between one transmission side (transmission station) and several receiving side (receiving station). 1 is a block diagram illustrating an example of a redundant system that performs optical transmission between a plurality of transmission sides (transmission stations) and one reception side (reception station), which is an optical signal transmission system of the present invention. 1 is a block diagram showing an example of a redundant system that performs optical transmission clockwise and counterclockwise between one transmitting side (transmitting station) and a plurality of receiving sides (receiving stations) in the optical signal transmission system of the present invention. The block diagram which shows an example of the redundancy in the conventional optical signal transmission system. FIG. 10 is a block diagram showing a redundancy example in the case of a conventional optical signal transmission system, in which the transmission side includes two or more transmission groups. Explanatory drawing which shows the relationship between the optical intensity and threshold value of the conventional optical signal transmission system (at the time of redundancy). Explanatory drawing which shows the relationship between the optical intensity and threshold value of the conventional optical signal transmission system (at the time of redundancy). Explanatory drawing which shows the relationship between the optical intensity and threshold value of the conventional optical signal transmission system (at the time of redundancy). Explanatory drawing which shows the relationship between the optical intensity and threshold value of the conventional optical signal transmission system (at the time of redundancy). Explanatory drawing which shows the relationship between the optical intensity and threshold value of the conventional optical signal transmission system (at the time of redundancy).

(Embodiment 1 of an optical signal transmission system)
An embodiment of the optical wavelength division multiplexing transmission system of the present invention will be described with reference to FIGS. This embodiment is an example of a case where serial digital data signals and the like based on information signals such as a plurality of digital video and audio signals are transmitted by optical wavelength multiplexing. As shown in FIG. 1, the basic configuration of this optical signal transmission system is to multiplex a large number of optical signals transmitted from a plurality of optical transmitters TX (λ ₁ ) to TX (λ _n ) by an optical wavelength multiplexer WDM. The multiplexed signal output from the optical transmission line is transmitted through an optical fiber (optical transmission line) L, the optical wavelength division multiplexed signal transmitted through the optical transmission line L is input to the optical wavelength demultiplexer WDM, and the separated optical signals are transmitted. Are transmitted to the optical receiver RX.

  The optical signal transmission system in FIG. 2 multiplexes a number of optical signals transmitted from a plurality of optical transmission devices TX (λ1) to TX (λn) that transmit optical signals of different wavelengths by an optical wavelength multiplexing device WDM. The multiplexed optical signal output from the wavelength multiplexing device WDM is branched by an optical branching device (coupler) C and transmitted using a plurality of optical transmission lines L, and wavelength-dependent by the optical wavelength separation devices WDM1, WDM2,. This is an optical signal transmission system that is separated into optical signals and input to the optical receiver RX2.

The optical signal transmission system of FIG. 3 has a plurality of optical transmission device groups TX1 (TX (λ ₁ ) to TX (λ _n )), TX2 (TX ( λ ₁ ) to TX (λ _n )),..., TXn (TX (λ ₁ ) to TX (λ _n )), and the optical transmission device groups TX 1, TX 2,. A plurality of combinations of optical wavelength multiplexers WDM1, WDM2,..., WDMn that wavelength-multiplex a plurality of optical signals λ _{1 to} λ _n output from WDM and output them as multiplexed optical signals, The multiplexed optical signals output from the respective sets of optical wavelength multiplexers WDM1, WDM2,..., WDMn are transmitted using a plurality of optical transmission lines L, and the optical wavelength demultiplexers WDM1, WDM2 for the respective groups are transmitted.・ ・ ・ ・ ・ ・ Optical reception by separating into optical signals by wavelength by WDMn An optical transmission system so as to enter the location RX2.

  2 and 3 use two or more optical wavelength demultiplexing devices WDM1, WDM2,..., WDMn, and the optical receiving device RX2 includes, for example, two or more optical input units 1 as shown in FIGS. Two or more optical wavelength separation devices WDM1, WDM2,..., WDMn are used to output optical signals λ1 to λn having different wavelengths, and among these optical signals, a plurality of optical signals having the same wavelength are output. The optical wavelength demultiplexers WDM1, WDM2,..., And WDMn and thereafter are made redundant by inputting to one optical receiver RX2. In this case, the optical signals input to the plurality of optical input units of the optical receiver RX2 are not optical signals of the same wavelength separated by the optical wavelength demultiplexers WDM1, WDM2,. It is also possible to input an optical signal having a wavelength corresponding to the optical signal.

  The optical receivers of the respective optical receivers RX2 in the optical signal transmission systems of FIGS. 2 and 3 determine the effectiveness of the optical signals input to the plurality of optical input units 1 (FIGS. 5 to 8), and are effective. A function of outputting a corresponding electrical signal and a function of having an electrical output are provided in accordance with information such as the priority order of a preset route from among the optical signals determined to be.

(Embodiment 1: Optical intensity detection for optical signal transmission system)
One embodiment of an optical receiver of the optical signal transmission system of the present invention is shown in FIG. This optical receiving apparatus is an example of the optical receiving apparatus RX2 of FIGS. 2 and 3, and is a system that detects the intensity of an optical signal and switches an output signal. An optical receiver RX2 shown in FIG. 5 converts an optical signal input to two or more optical input units 1 into an electrical signal by an optical / electrical conversion unit (PD) 2, and detects the intensity of the electrical signal by a detection unit 3. Then, the detected intensity is compared with a preset switching intensity (threshold value) by the control unit 5, and if it is larger than the threshold value, it is determined that the light input unit is effective. A function that can determine whether the part is not valid and is the same as the threshold value (can be set to either valid or not valid as required by the device when equivalent to the switching threshold value) Can also be provided. After the control unit 5, a switching unit 4-electric signal reclocking unit 7-electric signal drive unit 8-two electric output units 6 are provided.

  An optical adapter is mainly used for the two optical input units 1 in FIG. 5, and an optical cable is connected thereto. The photo / electric converter (Photo Diode: PD) 2 generates a photo current according to the light intensity when light is incident, and a pin diode (PIN-PD), an avalanche photodiode (APD) or the like is used. The The PD photocurrent detection circuit (for calculating the light intensity) 3 converts the intensity of the optical signal input to the optical input unit 1 by converting the photocurrent intensity generated in the PD based on the optical / electrical conversion efficiency. The light intensity information is calculated and sent to the control unit 5.

  The electric signal amplifying unit converts and amplifies the photocurrent obtained by the PD 2 into an intensity and format (single-end voltage output, differential voltage output, etc.) that can be transmitted as an electric signal. Can be converted and amplified multiple times. The single-ended electric signal is a signal that transmits information by voltage information (High / Low) between the signal line and GND, and the differential electric signal is information by voltage difference information (High / Low) between two signal lines. Is a signal to transmit.

  The control unit 5 in FIG. 5 compares the light intensity information obtained from the PD photocurrent detection unit 3 with a preset switching threshold intensity, and outputs an electrical signal input determined that the light intensity is valid. A command (command) is issued to the switching unit 4 so as to do so. The switching unit 4 outputs an electrical signal corresponding to a command from the control unit 5 among the plurality of input electrical signals. In addition to the above command, the control unit 5 can also control, as necessary, how the switching unit 4 should operate in various assumed states. If each system is valid, which one will be output first, and if each system is not valid, which one will be output first, the process when the original system is restored after switching to another system It is also possible to perform control such as management (automatically returning to the original system or continuing to output another system unless there is a manual command).

  The electric signal reclocking unit 7 in FIG. 5 is a waveform shaping unit, and the waveform of the signal transmitted through the optical transmission line is deteriorated as compared with that before transmission (the time fluctuation of the waveform occurs, Therefore, a clock with little temporal fluctuation is generated from the information included in the electrical signal, and the waveform of the electrical signal is reshaped based on this. Retake = Reclocking). The electric signal drive unit 8 takes in the signal after the reclocking and re-outputs it so as to satisfy the amplitude and the like that the electric signal output to the outside of the apparatus should have. A cable driver is used for SDI transmission. The electric signal reclocking unit 7 can be omitted when it is expected that the waveform deterioration is small.

  The electric output unit 6 shown in FIG. 5 outputs an electric signal that has been reshaped by the electric signal reclocking unit 7 and has an appropriate amplitude or the like by the electric signal driving unit 8. There may be provided a plurality of electrical output units.

(Embodiment 2 of optical receiver for optical signal transmission system: modulation component detection)
The optical receiver RX2 shown in FIG. 6 is also an example of the optical receiver RX2 of FIGS. 2 and 3, the basic configuration of FIG. 6 is the same as that of FIG. 5, and the difference is that the detector 3 of FIG. The PD photocurrent detection circuit is replaced with an electric signal modulation component detection unit. In FIG. 6, optical signals input to two or more optical input units 1 are converted into electric signals by an optical / electrical conversion unit (PD) 2 and serial digital based on information signals such as digital video and audio signals of the electric signals. Detects the modulation component (modulation intensity, etc.) of the data signal and sends the detection result to the control unit 5. The control unit 5 makes the modulation component effective based on the modulation component information obtained by the electric signal modulation component detection unit 3. The switching unit 4 is instructed to output the electrical signal input determined to be.

(Embodiment 3: Reclocking Detection of Optical Receiver for Optical Signal Transmission System)
Another embodiment of the optical receiver of the present invention is shown in FIG. This optical receiver is a method of switching the output signal by detecting the reclocked state of the electric signal. The basic configuration of FIG. 7 is the same as that of FIG. 6, and the difference is that in FIG. 7, the detection unit 3 is an electric signal reclocking state detection unit.

  The electric signal reclocking state detection unit 3 in FIG. 7 has a function similar to or the same as that of the electric signal reclocking unit 7 in FIG. 5, and the waveform of the digital signal transmitted through the optical transmission line L is transmitted before transmission. Compared to the information contained in the electrical signal, a clock with less temporal fluctuation is generated from the information that is degraded (time fluctuation of the waveform has occurred and the timing of the signal is not appropriate). The waveform of the electric signal is reshaped based on the above (retiming the timing = reclocking). In this case, reshaping may not be possible if the waveform deterioration is large. It has a function of observing the success or failure of this process (whether it could be reshaped or not) and sending the result to the control unit 5. The control unit 5 in FIG. 7 instructs the switching unit 4 to output an electrical signal corresponding to the optical signal determined to be valid based on the information on the reclocked state obtained from the electrical signal reclocked state detecting unit 3. Is what you do.

(Embodiment 4: Optical Detection Device for Optical Signal Transmission System: Error Detection)
Another embodiment of the optical receiver for the optical signal transmission system of the present invention is shown in FIG. This optical receiver is a system that detects an error of an electric signal and switches an output signal. In FIG. 8, there are two optical signal transmission paths, each of which includes an optical input unit 1, a PD 2, an electric signal amplification unit, a serial / parallel conversion unit 10, and a parallel / serial conversion unit 11. Is an error detection unit, and a control unit 5 is provided between the two error detection units 3.

  The serial / parallel converter 10 is for converting serial data into parallel data. If the optical signal input to the optical receiver is serial data, but the original information source is parallel data, the bit error rate (how many bit errors out of the total number of bits of data to be transmitted) In many cases, it is not possible to observe whether or not a data error has occurred, or the like, and serial data may be converted into parallel data. In this case, the serial / parallel converter 10 shown in FIG. 8 is required. The reason why the bit error rate is “similar information” in the above is because there is an observation method of error seconds (how many seconds an error has occurred during the total transmission time) in addition to the bit error rate. If it is possible to observe whether a bit error rate or a data error has occurred in the serial data, the serial / parallel converter 10 shown in FIG. 8 can be omitted. Here, serial data is basically a single-end electrical signal / differential electrical signal, etc. that transmits one type of information over time, and parallel data contains multiple information over time. This is the data of the transmission method (data method in old printer cables).

  The error detection unit (error rate detection unit) 3 in FIG. 8 generates information similar to the bit error rate of the electrical signal (how many bit errors have occurred in the total number of bits of data to be transmitted) or a data error. It is detected whether or not it has been sent and sent to the control unit 5.

  The parallel / serial converter 11 shown in FIG. 8 reconverts into a serial signal suitable for transmission when the serial / parallel converter 10 shown in FIG. 8 performs parallel conversion so that the error rate detector 3 detects an error. There is a need. That is, it is for converting parallel data into serial data. If it is possible to observe whether a bit error rate or a data error has occurred in the serial data, the parallel / serial converter 11 can be omitted.

  The control unit 5 in FIG. 8 instructs the switching unit 4 to output an electric signal input determined to be valid based on the error occurrence state or information similar to the bit error rate obtained from the error rate detection unit 3. It is a part to do.

  6 to 8, like the control unit 5 in FIG. 5, in addition to the command, it is necessary for the switching unit 4 to operate in various assumed states. It can be controlled accordingly. If each system is valid, which one will be output first, and if each system is not valid, which one will be output first, the process when the original system is restored after switching to another system It is also possible to perform control such as management (automatically returning to the original system or continuing to output another system unless there is a manual command).

(Reference example of optical signal transmission system without optical wavelength multiplexing)
In a system in which optical wavelength multiplexing is not performed as shown in FIG. 4, optical signals output from a plurality of optical transmission devices (TX) sharing a signal source that can be operated in the same or alternative manner in a plurality of optical input units of the optical reception device RX2. Enter.

(Embodiment 1 of redundancy of optical signal transmission system)
Figure 10 is one transmitting (transmitting station: Z stations) 20 to be wavelength-multiplexed the converted plurality of optical signals lambda ₁ to [lambda] _n optical transmitter TX of Figures 1-3 and by the optical transmitter TX An optical wavelength multiplexer WDM and a coupler C for outputting as multiplexed optical signals are provided, and a coupler C, an optical wavelength demultiplexer WDM, and an optical receiver RX2 are provided on each of a plurality of receiving sides (receiving stations: A station to G station) 21. Two optical transmission lines L are wired between the coupler C of the transmitting station (Z station) 20 and the couplers of the respective receiving stations (A station to G station) 21 for redundancy. The optical receiver for the optical signal transmission system according to any of the embodiments shown in FIGS. 5 to 8 can be used as the optical receiver RX2 of the receiving station (A station to G station) 21.

  In the optical signal transmission system of FIG. 10, the optical wavelength multiplexed signal transmitted from the transmitting station (Z station) 20 is received by each optical receiving device RX2 of the receiving station (A station to G station) 21 (FIGS. 5 to 8). All or part of the input optical signal information such as light intensity, modulation component, amplitude, timing accuracy, signal transmission speed, reclocking state, error rate, etc. by the detecting unit 3 of each optical receiving device RX2 Is detected, the validity of the input optical signal is determined based on the detected input optical signal information, and an electrical signal corresponding to the input optical signal determined to be valid is selected and output.

(Embodiment 2 of redundancy of optical signal transmission system)
FIG. 11 shows the wavelengths of the optical transmission device TX of FIGS. 1 to 3 and the optical signals λ _{1 to} λ _n converted by the optical transmission device TX to a plurality of transmission sides (transmission stations: B station to K station) 20. An optical wavelength multiplexing device WDM that multiplexes and outputs as a multiplexed optical signal is provided, an optical wavelength demultiplexing device WDM and an optical receiving device RX2 are provided on one receiving side (receiving station: A station) 21, and a transmitting station (B station to Two optical transmission lines L are wired between the K station) 20 and the receiving station (A station) 21 for redundancy. The optical receiver for the optical signal transmission system according to any one of FIGS. 5 to 8 can be used as the optical receiver RX2 of the receiving station (A station) 21. The operation of this optical signal transmission system is the same as that in the first embodiment.

(Embodiment 3 of redundancy of optical signal transmission system)
In FIG. 12, one transmitter (transmitting station: A station) 20 wavelength-multiplexes the optical transmitter TX of FIGS. 1 to 3 and a plurality of optical signals λ _{1 to} λ _n converted by the optical transmitter TX. An optical wavelength multiplexing device WDM for outputting as a multiplexed optical signal is provided, and an optical wavelength demultiplexing device WDM and an optical receiving device RX2 are arranged on each of a plurality of receiving sides (receiving stations: B station to K station) 21, and a transmitting station ( Two optical transmission lines L are wired between the coupler C of the A station) 20 and the respective receiving stations (B station to K station) 21 for redundancy. The optical receiver for the optical signal transmission system according to any of the embodiments shown in FIGS. 5 to 8 can be used as the optical receiver RX2 of the receiving station (B station to K station) 21. In the optical signal transmission system of FIG. 12, one optical transmission path is used as a clockwise main trunk line, and the other optical transmission path is used as a counterclockwise main trunk line (counterclockwise).

  The operation of the optical receiver for the optical signal transmission system in FIGS. 9 to 12 is the same as the operation of the optical receiver for the optical signal transmission system in FIGS.

DESCRIPTION OF SYMBOLS 1 Optical signal input part 2 Optical / electrical conversion part 3 Detection part 4 Switch 5 Control part 6 Electric output part 7 Electric signal reclocking part 8 Electric signal drive part 10 Serial / parallel conversion part 11 Parallel / serial conversion part 12 Reclocking state detection Section 20 Transmitting station 21 Receiving station C Coupler L Optical transmission line

Claims (15)

An optical transmitter (TX) having an electrical / optical converter that converts a plurality of serial digital data signals into a plurality of optical signals having wavelengths suitable for optical wavelength multiplexing, and a plurality of signals converted by the optical transmitter (TX) An optical wavelength multiplexing device (WDM) that wavelength-multiplexes an optical signal and outputs it as a multiplexed optical signal, an optical wavelength separation device (WDM) that separates the multiplexed optical signal into a plurality of optical signals, and the multiplexed optical signal propagates In an optical signal transmission system comprising: an optical transmission line, and an optical receiver (RX) having an optical / electrical converter that converts a plurality of optical signals separated by the optical wavelength separation device (WDM) into an electrical signal,
The optical receiver (RX) includes two or more optical signal input units (1), optical / electrically converts two or more optical signals input to the optical signal input unit (1), and converts them into converted electrical signals. And detecting all or part of the input optical signal information such as intensity, modulation component, amplitude, timing accuracy, signal transmission speed, reclocking state, error rate of each of the two or more input optical signals, and the detected input light An optical signal transmission system, wherein the validity of an input optical signal is determined based on signal information, and an electrical signal corresponding to the input optical signal determined to be valid is selected and output. The optical signal transmission system according to claim 1.
Generate a clock with little temporal fluctuation from the information contained in the selected and output electrical signal, reshape the waveform of the electrical signal based on that clock, and satisfy the required amplitude of the electrical signal The optical signal transmission system is characterized in that the signal is output again to the outside.   3. The optical signal transmission system according to claim 1, wherein an optical transmission device (TX) and an optical wavelength multiplexing device (WDM) are arranged in a transmission station, and an optical reception device (RX) and an optical wavelength separation device (WDM). ) Is arranged in the receiving station, and can transmit an optical signal between the transmitting station and the receiving station.   The optical signal transmission system according to any one of claims 1 to 3, wherein an optical signal input to two or more optical signal input units (1) of an optical receiver (RX) and a transmission source of the optical signal One or more of an optical transmitter (TX), an optical wavelength multiplexer (WDM), an optical wavelength demultiplexer (WDM) arranged in the optical signal path, and / or an optical transmission path for transmitting multiplexed optical signals An optical signal transmission system characterized in that is made redundant.   4. The optical signal transmission system according to claim 1, wherein an optical signal transmitted from the optical transmission device (TX) is transmitted in the same direction or the reverse direction to the redundant optical transmission line. An optical signal transmission system.   6. The optical signal transmission system according to claim 1, wherein the optical receiver (RX) selects an electrical signal corresponding to an input optical signal determined to be valid from two or more electrical signals. The optical signal transmission system is selected according to a preset priority of the input unit.   6. The optical signal transmission system according to claim 1, wherein the optical receiver (RX) selects an electrical signal corresponding to an input optical signal determined to be valid from two or more electrical signals. An optical signal transmission system characterized in that, in addition to a preset priority of the input unit, the currently selected input unit is maintained if it is valid. In the optical receiver of the optical signal transmission system according to any one of claims 1 to 7,
The optical receiver (RX) includes two or more optical signal input units (1), an optical / electrical conversion unit (2) for O / E converting optical signals input to the respective optical signal input units (1), Detection that detects all or part of optical signal information such as intensity, modulation component, amplitude, timing accuracy, signal transmission speed, reclocking state, error rate of each of the two or more input optical signals based on the converted electrical signal Unit (3), a switch (4) for switching and outputting the electrical signal converted by the optical / electrical converter (2), and two or more electrical signals converted by the optical / electrical converter (2) Of these, the validity of each input optical signal is determined based on the optical signal information detected by the detection unit (3), and an electrical signal corresponding to the input optical signal determined to be valid is selected and the electrical signal is output. Control unit (4) for switching and controlling the switch (4) ) And, switch (4) an optical signal transmission system for optical receiver, characterized in that the electrical signal is output with an electrical output unit (6) output from. The optical receiver for an optical signal transmission system according to claim 8,
On the output side of the switch (4), an electrical signal reclocking unit (7) that generates a clock with little temporal fluctuation from information contained in the electrical signal and reshapes the waveform of the electrical signal based on the generated clock.
And an electric signal drive unit (8) for re-outputting using an electric signal amplitude means so that an electric signal output to the outside satisfies a required amplitude, or the electric signal drive unit (8). An optical receiver for an optical signal transmission system. In the optical receiver for an optical signal transmission system according to claim 8 or 9,
The detection unit (3) is a light intensity detection unit that detects the light intensity of the electric signal converted by the light / electric conversion unit (2), and the control unit (5) adjusts the intensity detected by the light intensity detection unit. A light for an optical signal transmission system, wherein an electrical signal corresponding to an optical signal determined to be effective based on the electrical signal is selected and the switch (4) is controlled to be output so that the electrical signal is output. Receiver device. In the optical receiver for an optical signal transmission system according to claim 8 or 9,
The detection unit (3) is a modulation component detection unit that detects a modulation component of the electrical signal converted by the optical / electrical conversion unit (2), and the control unit (5) is a modulation component detected by the modulation component detection unit. Based on the information, the effectiveness of the modulation component is judged and an electrical signal corresponding to the optical signal judged to be valid is selected, and the switch (4) is switched and controlled so that the electrical signal is output. An optical receiver for an optical signal transmission system. In the optical receiver for an optical signal transmission system according to claim 8 or 9,
The detection unit (3) is a reclocking state detection unit that detects the reclocking state of the electrical signal converted by the optical / electrical conversion unit (2), and the control unit (5) is obtained from the reclocking state detection unit (12). Based on the reclocked state information, the validity of the reclocked state is determined, the electrical signal corresponding to the optical signal determined to be valid is selected, and the switch (4) is switched and controlled so that the electrical signal is output. What is claimed is: 1. An optical receiver for an optical signal transmission system. In the optical receiver for an optical signal transmission system according to claim 8 or 9,
A serial / parallel converter (10) for serial / parallel conversion of the electrical signal converted by the optical / electric converter (2) and a parallel / serial converter (11) are provided, and the detector (3) is serial / parallel. The error detection unit detects error information such as a bit error rate and a data error of the parallel signal converted by the conversion unit (10), and the control unit (5) detects an error occurrence state or a bit error rate obtained from the error detection unit. The switch (4) is switched and controlled so that the electrical signal corresponding to the optical signal determined to be valid is selected by judging the validity of the bit error based on the similar information and the electrical signal is output. An optical receiver for an optical signal transmission system.   14. The optical receiver for an optical signal transmission system according to claim 8, wherein an electric signal corresponding to an input optical signal determined to be valid by the control unit (5) among two or more electric signals. An optical receiver for an optical signal transmission system, having a function of selecting according to a preset priority of an input unit when selecting.   14. The optical receiver for an optical signal transmission system according to claim 8, wherein an electric signal corresponding to an input optical signal determined to be valid by the control unit (5) among two or more electric signals. An optical receiver for an optical signal transmission system having a function of maintaining the state of a currently selected input unit if the currently selected input unit is valid, in addition to the priority of the input unit set in advance. .

Images