JP2011041175A - Optical transmission system, device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission system, an optical transmission device, and an optical transmission method which transmit a signal from an optical transmission device split by an optical splitter as light itself without OEO conversion to the utmost. <P>SOLUTION: When there is no electrical signal in an additional electrical buffer 24, a determination control circuit 25 sets an optical gate 28 at transmission, and at the same time, stops operation of an optical transmitter 26 for transmitting an optical signal from an optical transmission device 10. When an electrical signal arrives at the additional electric buffer 24 before header information of an optical signal from the optical transmission device 10 received by an optical receiver 22 is read, and when an electric signal arrives at the additional electric buffer 24 before an optical signal from the optical transmission device 10 passes through the optical gate 28, an electrical signal is read from the additional electric buffer 24 immediately after an optical signal from the optical transmission device 10 passes through the optical gate 28, and operation of an optical transmitter 26 is started simultaneously when the optical gate 28 is set at non-transmission. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical transmission system, an optical transmission apparatus, and an optical transmission method that provide two transmission routes: a route that does not perform OEO conversion and a route that performs OEO conversion.

  In recent years, OEO (Optical-Electrical-Optical-Optical) for avoiding transmission delay due to electrical processing such as routing that occurs in transmission devices in relay networks and reducing the scale of transmission device processing units as the traffic volume on the Internet increases. Research on photonic networks that do not perform conversion has been actively conducted (see Non-Patent Document 1). However, in photonic networks using optical packet switching technology, it is difficult to realize an optical buffer, so in future networks, not all will be replaced by photonic networks, but existing networks based on electrical processing. It is considered that these photonic networks will coexist.

  FIG. 4 shows a configuration example of an optical transmission system having a function of performing OEO conversion based on the above background and a function of transmitting light as it is without performing OEO conversion. The optical transmission system illustrated in FIG. 4 includes an optical transmission device 110, an optical reception device 130, and an optical transmission device 120 connected between the optical transmission device 110 and the optical reception device 130. The optical transmission device 120 includes an optical splitter 121 that branches the optical signal from the optical transmission device 110, an optical receiver 122 that receives the branched optical signal and converts it into an electrical signal, and an electrical signal from the optical receiver 122. An electric buffer 123 for storing, an additional electric buffer 124 for storing a signal received from another optical transmission device other than the optical transmission device 120 or another network, and to be sent to the optical receiving device 130; an electric signal of the electric buffer 123; A determination control circuit 125 that reads an electrical signal from the buffer 124, an optical transmitter 126 that converts the electrical signal read by the determination control circuit 125 into an optical signal, and transmits the optical signal. An optical delay that transmits the optical signal branched by the optical splitter 121. An optical gate 128 for transmitting / not transmitting an optical signal from the optical delay line 127, an optical signal from the optical transmitter 126, and an optical gate. It constituted by an optical splitter 129 for coupling optical signals from the 28.

  Here, after being branched by the optical splitter 121, the route of the optical receiver 122 → the electric buffer 123 → the determination control circuit 125 → the optical transmitter 126 is a route for performing OEO conversion, and after being branched by the optical splitter 121. The route from the optical delay line 127 to the optical gate 128 is a route for transmitting light without performing OEO conversion. Further, the optical transmitter 126 outputs an optical signal having the same wavelength as the wavelength of the optical signal transmitted through a route that does not perform OEO conversion.

  When the optical signal from the optical transmitter 110 is transmitted, the determination control circuit 125 sets the optical gate 128 to be transparent, and at the same time stops the operation of the optical transmitter 126 and makes the optical signal from the optical transmitter 110 non-transparent. In this case, the optical gate 128 is set to be non-transparent, and at the same time, the operation of the optical transmitter 126 is started. The optical delay line 127 is used for delaying the optical signal by a time necessary for the determination control circuit 125 to select transmission / non-transmission of the optical signal from the optical transmission device 110. Designed to be as short as possible for transmission to delay.

  As an example of the operation of the optical transmission apparatus 120, for example, when there is an electric signal in the additional electric buffer 124, when control is performed to select a route for performing OEO conversion, the determination control circuit 125 causes the electric buffer 123 and the additional electric buffer 120 to By performing the process of reading the electrical signal from the buffer 124, it becomes possible to add a signal in the optical transmission apparatus 120. When there is no electrical signal in the additional electrical buffer 124, control is performed to select a route that does not perform OEO conversion. Thus, transmission delay due to electrical processing can be avoided.

  By performing control based on the configuration as described above, it is possible to realize an optical transmission system in which an optical signal having the same wavelength is transmitted, and a function that performs OEO conversion and a function that does not perform OEO conversion coexist. it can.

  As a signal reading method of the determination control circuit 125 in the optical transmission apparatus 120, there is a FIFO (first-in first-out) method for reading out signals in the order of arrival as described in Non-Patent Document 2. In the FIFO method, electrical signals that arrive at the electrical buffer 123 and the additional electrical buffer 124 are read out by the determination control circuit 125 in the order of arrival and transmitted to the optical transmitter 126.

  The selection operation of transmission / non-transmission of the optical signal from the optical transmission device 110 in the determination control circuit 125 when the above-described FIFO method is adopted will be described in detail with reference to FIG. The signals A1 to A4 shown in FIG. 5 are the signal transmitted to the optical gate 128 and the signal transmitted to the electric buffer 123 in the optical transmission device 120 of FIG. 4, and the signals B1 to B3 are the additional electric buffer. This signal is transmitted to 124. In the FIFO method, since signals are read out in the order of arrival, the signals are read out in the order of B1 → A1 → B2. Here, since the signal A1 overlaps with the signal B1 in time, a route passing through the optical gate 128 (a route not subjected to OEO conversion) cannot be selected.

  Since the signal A2 transmitted next to the signal B2 is not present in the additional electrical buffer 124, the determination control circuit 125 does not read the signal A2 and transmits it through a route that passes through the optical gate 128 (route that does not perform OEO conversion). Is done.

  The signals B3, A3, and A4 transmitted next are read out in the order of B3 → A3 → A4 in the order of arrival. Here, since the signal A3 overlaps with the signal B3 in time, a route that passes through the optical gate 128 (a route that does not perform OEO conversion) cannot be selected. Since there is no signal in the additional electrical buffer 124, the signal A4 seems to be able to be transmitted through a route passing through the optical gate 128 (a route not performing OEO conversion), but the signal A3 is read by the signal B3. Since it is necessary to wait in the electric buffer 123 until completion, if the signal A4 is transmitted along the route passing through the optical gate 128, it overlaps with the signal A3. For this reason, the signal A4 must also be transmitted through a route for performing OEO conversion.

  From the above, it is necessary to perform OEO conversion in the optical transmission device 120. (1) When an optical signal arrives at the electric buffer 123 during the reading process of the electric signal of the additional electric buffer 124, (2) When a new optical signal arrives at the electrical buffer 123 during the process of reading out the electrical signal from the buffer 123, two states occur.

  Here, the problem with the FIFO method is that it is necessary to perform OEO conversion on the signal branched by the optical splitter 121 when the state (1) or (2) is reached. If the signal branched by the optical splitter 121 can be transmitted as light without OEO conversion utilizing the characteristics of the photonic network, transmission delay due to electrical processing can be avoided. Therefore, it is desirable not to perform OEO conversion as much as possible.

  In addition, as another signal readout method of the determination control circuit 125 in the optical transmission apparatus 120, when the state (1) described above is reached, the readout of the electrical signal from the additional electrical buffer 124 is stopped, and the optical splitter 121 A method in which the branched signal is always preferentially transmitted through a route passing through the optical gate 128 is also conceivable. In this method, since the signal branched by the optical splitter 121 is not stored in the electric buffer 123, the state (2) described above is not caused. In this method, since the signal branched by the optical splitter 121 can always be transmitted as light without OEO conversion, the above-mentioned problem of the FIFO method can be solved. As long as the signal branched by the optical splitter 121 is transmitted, the signal needs to be kept waiting in the additional electric buffer 124, thereby causing a delay problem and increasing the buffer size of the additional electric buffer 124. . In addition, the processing is stopped during the reading of the electric signal of the additional electric buffer 124 so that the signal branched by the optical splitter 121 passes through the optical gate 128. It becomes necessary to design the line 127 to be long, which is contrary to the purpose of transmitting an optical signal with as low delay as possible without converting it into an electric signal.

  Furthermore, as another application of the signal readout method described above, weighting is performed on the rate of reading the electrical signal of the additional electrical buffer 124 and the rate at which the signal branched by the optical splitter 121 is transmitted through the route through the optical gate 128, Even when the signal branched by the optical splitter 121 is transmitted, a method of avoiding the problem of waiting in the additional electric buffer 124 by reading out the electric signal of the additional electric buffer 124 at a constant rate is conceivable. However, in this method, there is no problem when the transmission band is constant, but the above-described weighting ratio needs to be changed every time the transmission band is changed, so that the control becomes complicated.

S.J.Ben Yoo, “Optical Packet and Burst Switching Technologies for the Future Photonic Internet,” Journal Lightwave Technology, Vol. 24, No. 12, pp. 4468-4492, December 2006. Takahashi Takataka, Yamamoto Naoyo, Yoshino Hideaki, Toda Akira, “Intuitive queuing system”, IEICE, 2003.

  The present invention has been made based on the background as described above, and an object of the present invention is to transmit a signal from an optical transmission device branched by an optical splitter as light as possible without OEO conversion. Thus, an object of the present invention is to provide an optical transmission system, an optical transmission apparatus, and an optical transmission method that can reduce the probability that OEO conversion needs to be performed.

  In order to achieve the above object, the present invention comprises an optical transmission device, an optical reception device, and an optical transmission device connected between the optical transmission device and the optical reception device, wherein the optical transmission device is An optical splitter for branching an optical signal from the optical transmitter, an optical receiver for receiving one of the branched optical signals, an electrical buffer for storing an optical receiver signal, and the optical transmitter An additional electrical buffer for storing a signal to be added to the optical signal of the optical signal; reading header information of the optical signal received by the optical receiver to determine transmission / non-transmission of the optical signal; and the electrical buffer and the additional electrical buffer A determination control circuit that reads an electric signal from the optical signal, an optical transmitter that converts the electric signal read from the determination control circuit into an optical signal and transmits the optical signal, and light that transmits the other optical signal among the branched optical signals Delay line and light In the optical transmission system comprising: an optical gate that transmits / non-transmits an optical signal from a wire; and an optical splitter that combines the optical signal from the optical transmitter and the optical signal from the optical gate, the determination control When there is no electrical signal in the additional electrical buffer, the circuit sets the optical gate to be transparent and simultaneously stops the operation of the optical transmitter to transmit the optical signal from the optical transmitter, The additional signal is received when an electric signal arrives at the additional electric buffer before the received header information of the optical signal from the optical transmitter is received and until the optical signal from the optical transmitter is completely transmitted through the optical gate. When an electrical signal arrives at the electrical buffer, the electrical signal is read from the additional electrical buffer immediately after the optical signal from the optical transmission device passes through the optical gate. Performed, and performs an operation start simultaneously the optical transmitter by setting the optical gate non-transparent.

  The optical delay line may be configured such that the determination control circuit reads the header information of the optical signal to determine transmission / non-transmission of the optical signal and delays the optical signal by a time necessary for performing the control. preferable.

  The present invention also provides an optical transmission device connected between an optical transmission device and an optical reception device, an optical splitter for branching an optical signal from the optical transmission device, and one of the branched optical signals. An optical receiver that stores the signal of the optical receiver, an additional electrical buffer that stores a signal to be added to the optical signal from the optical transmitter, and a header of the optical signal received by the optical receiver A determination control circuit that reads information to determine transmission / non-transmission of an optical signal and reads an electrical signal from the electrical buffer and the additional electrical buffer, and an electrical signal read from the determination control circuit is converted into an optical signal An optical transmitter that converts and transmits, an optical delay line that transmits the other optical signal among the branched optical signals, an optical gate that transmits / non-transmits an optical signal from the optical delay line, and the optical transmission Optical signal from the instrument An optical splitter for combining optical signals from the optical gate, and when the determination control circuit does not have an electrical signal in the additional electrical buffer, the optical gate is set to be transmissive and simultaneously the operation of the optical transmitter. When the electrical signal arrives at the additional electrical buffer until the optical signal from the optical transmission device is stopped and the optical signal from the optical transmission device received by the optical receiver is read, and When the electrical signal arrives at the additional electrical buffer before the optical signal from the optical transmission device has been transmitted through the optical gate, the additional electrical buffer is transmitted immediately after the optical signal from the optical transmission device is transmitted through the optical gate. An electrical signal is read from the buffer, the optical gate is set to non-transparent, and the operation of the optical transmitter is started at the same time.

  The optical delay line may be configured such that the determination control circuit reads the header information of the optical signal to determine transmission / non-transmission of the optical signal and delays the optical signal by a time necessary for performing the control. preferable.

  The present invention is also directed to an optical transmission method for an optical transmission apparatus connected between an optical transmission apparatus and an optical reception apparatus, when there is no signal to be added to the optical signal from the optical transmission apparatus. / By setting the optical gate that performs non-transmission to transmission, transmitting the optical signal from the optical transmission device to the optical reception device, until the header information of the optical signal from the optical transmission device is read, When a signal to be added to the optical signal from the optical transmission device arrives, and until the optical signal from the optical transmission device finishes passing through the optical gate, it is added to the optical signal from the optical transmission device. When a power signal arrives, a signal to be added to the optical signal from the optical transmitter is transmitted to the optical receiver immediately after the optical signal from the optical transmitter has passed through the optical gate. And

  As described above, according to the present invention, even when there is an electrical signal in the additional electrical buffer, when the electrical signal arrives at the additional electrical buffer before reading the header information of the optical signal from the optical transmitter, If the electrical signal arrives at the additional electrical buffer before the optical signal from the transmission device has passed through the optical gate, the electrical signal is read from the additional electrical buffer immediately after the optical signal from the optical transmission device has passed through the optical gate. Thus, since the light is transmitted without any OEO conversion as much as possible, the probability that the OEO conversion needs to be performed can be reduced.

It is a figure which shows the whole structure of the optical transmission system of this invention. It is a figure explaining the optical transmission method in the optical transmission system shown in FIG. It is a figure which shows the example of a ratio which performs OEO conversion when the optical transmission method of this invention is implemented, and when the conventional FIFO system is implemented. It is a figure which shows the whole structure of the conventional optical transmission system. It is a figure explaining the transmission / non-transmission selection operation | movement of the optical signal from the optical transmitter in the conventional optical transmission system.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an optical transmission system according to the present invention. The optical transmission system illustrated in FIG. 1 includes an optical transmission device 10, an optical reception device 30, and an optical transmission device 20 connected between the optical transmission device 10 and the optical reception device 30. The optical transmission apparatus 20 includes an optical splitter 21 that branches an optical signal from the optical transmission apparatus 10 and an optical receiver that receives one of the optical signals branched by the optical splitter 21 and converts it into an electrical signal. 22, an electrical buffer 23 for storing an electrical signal output from the optical receiver 22, and a signal (optical transmission) received from an optical transmission device other than the optical transmission device 20 or another network and to be transmitted to the optical reception device 30. An additional electrical buffer 24 that stores a signal to be added to the optical signal from the apparatus 10, the header information of the optical signal received by the optical receiver 22 is read to determine whether the optical signal is transmitted or not, and the electrical buffer 23 A determination control circuit 25 that reads an electric signal from the additional electric buffer 24, an optical transmitter 26 that converts the electric signal read from the determination control circuit 25 into an optical signal, and transmits the optical signal; , The optical delay line 27 that transmits the other optical signal, the optical gate 28 that transmits / non-transmits the optical signal from the optical delay line 27, and the light from the optical transmitter 26. The optical splitter 29 is configured to combine the signal and the optical signal from the optical gate 28.

  After branching by the optical splitter 21, the route of the optical receiver 22 → the electric buffer 23 → the determination control circuit 25 → the optical transmitter 26 is a route for performing the OEO conversion. The route from the line 27 to the optical gate 28 is a route for transmitting light without performing OEO conversion. Further, the optical transmitter 26 outputs an optical signal having the same wavelength as the wavelength of the optical signal transmitted through a route that does not perform OEO conversion.

When the optical signal from the optical transmitter 10 is transmitted (when OEO conversion is not performed), the determination control circuit 25 sets the optical gate 28 to be transparent and simultaneously stops the operation of the optical transmitter 26 to thereby transmit the optical transmitter. When the optical signal from 10 is made non-transparent (when OEO conversion is performed), control is performed so that the operation of the optical transmitter 26 is started simultaneously with setting the optical gate 28 non-transparent.
Further, when there is no electrical signal in the additional electrical buffer 24, the determination control circuit 25 sets the optical gate 28 to be transparent and simultaneously stops the operation of the optical transmitter 26, and converts the optical signal from the optical transmission device 10 into an electrical signal. The signal is transmitted with low delay without being converted into a signal.
Further, the determination control circuit 25 receives the electric signal that has arrived at the additional electric buffer 24 before reading the header information of the optical signal from the optical transmission device 10 received by the optical receiver 22 and the optical signal from the optical transmission device 10. The electrical signal that has arrived at the additional electrical buffer 24 until it has passed through the optical gate 28 is read out immediately after the optical signal from the optical transmission device 10 has passed through the optical gate 28, and at the same time, the optical gate 28 is made non-transmissive. After setting, the operation of the optical transmitter 26 is started, and the optical signal from the optical transmission device 10 is transmitted as much as possible even when there is an electric signal in the additional electric buffer 24.

The optical delay line 27 is a time required for the determination control circuit 25 to read the header information of the optical signal received by the optical receiver 22 to determine transmission / non-transmission of the optical signal and perform control, Arranged to delay the optical signal.
The signal received by the optical receiver 22 is simultaneously sent to the electric buffer 23 and the determination control circuit 25. The electric buffer 23 accumulates the header information and payload information of the signal, and the determination control circuit 25 sends the signal. Only the header information at the head of the received signal is read to determine control. In this way, by sending the header information to the determination control circuit 25 without going through the electric buffer 23, the determination process is performed immediately, so that the optical delay line 27 can be shortened. Only header information may be sent directly from the optical receiver 22 to the determination control circuit 25.

  When the OEO conversion is not performed, the optical delay line 27 is delayed by the processing time of the header information of the signal received by the optical receiver 22. On the other hand, when performing OEO conversion, both header information and payload information are read from the electrical buffer 23 and a signal is transmitted to the optical transmitter 26, so that the modulation processing time of the optical transmitter 26 is negligibly short. Even in this case, the processing time of both the header information and the payload information is delayed as compared with the case where the OEO conversion is not performed. Therefore, when OEO conversion is not performed, transmission through the optical delay line 27 can be performed with a lower delay than when OEO conversion is performed.

FIG. 2 is a diagram for explaining an optical transmission method in the optical transmission apparatus shown in FIG. 2 are the signal transmitted to the optical gate 28 and the signal transmitted to the electrical buffer 23 in the optical transmission apparatus 20 of FIG. 1, and the signals B1 to B3 are the additional electrical buffer. This signal is transmitted to 24.
In the optical transmission method of the present invention, the electric signal that has arrived at the additional electric buffer 24 until the header information of the optical signal received by the optical receiver 22 is read, and the additional electric buffer until the optical signal has passed through the optical gate 28. The determination control circuit 25 reads out the electrical signal that has arrived at 24 immediately after the optical signal has passed through the optical gate 28. Since the signal B1 and the signal B2 are signals of the additional electric buffer corresponding to the above condition with respect to the signal A1, the signal A1 is read from the additional electric buffer 24 immediately after passing through the optical gate.

  The signal A2 transmitted next to the signal B2 is transmitted through a route that does not perform OEO conversion through the optical gate 28 because there is no signal of the additional electrical buffer that satisfies the above-described conditions.

  The signal B3, the signal A3, and the signal A4 that are transmitted next are added to the signal B3 immediately after the signal A3 passes through the optical gate because the signal B3 is a signal of an additional electric buffer that satisfies the above-described conditions. Read from the electrical buffer 24. The signal A4 overlaps in time with the signal B3 because the signal B3 is read immediately after the signal A3. For this reason, the signal A4 is read after the signal B3 because the signal A4 is in the state (1) described above (the optical signal has arrived at the electric buffer during the reading process of the electric signal of the additional electric buffer).

  When comparing the behavior of the signals A1 to A4 by the optical transmission method described above with the behavior of the signals A1 to A4 by the conventional FIFO method shown in FIG. 5, in FIG. 5, only the signal A2 is not subjected to OEO conversion. In FIG. 2, the signals A1 to A3 are transmitted through a route that does not perform OEO conversion. Therefore, according to the optical transmission method of the present invention, it is possible to reduce the probability that OEO conversion needs to be performed as compared with the prior art.

  FIG. 3 is a diagram showing an example of a ratio for performing OEO conversion when the optical transmission method of the present invention is implemented and when the conventional FIFO method is implemented. FIG. 3 assumes that each signal arriving at the optical gate 28, the electrical buffer 23, and the additional electrical buffer 24 follows a Poisson process. In the optical transmission apparatus 20 that handles a transmission band of 1 Gbit / s in total, the optical gate 28, electrical When the transmission band of the signal arriving at the buffer 23 is 256 Mbit / s, the ratio of performing the OEO conversion when the transmission band of the signal arriving at the additional electric buffer 24 is changed from 128 Mbit / s to 744 Mbit / s is a numerical value. It is obtained by calculation. All numerical calculations were performed on the assumption that an Ethernet (registered trademark) packet signal (frame length 64 bytes) was transmitted.

  From FIG. 3, it can be understood that the ratio of OEO conversion is reduced by performing the optical transmission method of the present invention as compared with the conventional FIFO method. Therefore, according to the optical transmission method of the present invention, it is possible to reduce the probability that OEO conversion needs to be performed as compared with the conventional case.

10, 110 Optical transmitter 20, 120 Optical transmitter 21, 121 Optical splitter 22, 122 Optical receiver 23, 123 Electrical buffer 24, 124 Additional electrical buffer 25, 125 Judgment control circuit 26, 126 Optical transmitter 27, 127 Optical Delay line 28, 128 Optical gate 29, 129 Optical splitter 30, 130 Optical receiver

Claims (5)

An optical transmission device, an optical reception device, and an optical transmission device connected between the optical transmission device and the optical reception device,
An optical splitter for branching an optical signal from the optical transmitter; an optical receiver for receiving one of the branched optical signals; an electrical buffer for storing the signal of the optical receiver; An additional electric buffer for storing a signal to be added to the optical signal from the optical transmission device; reading the header information of the optical signal received by the optical receiver to determine transmission / non-transmission of the optical signal; and And a determination control circuit that reads an electric signal from the additional electric buffer, an optical transmitter that converts the electric signal read from the determination control circuit into an optical signal, and transmits the optical signal, and the other of the branched optical signals An optical delay line that transmits a signal, an optical gate that transmits / non-transmits an optical signal from the optical delay line, and an optical splitter that combines the optical signal from the optical transmitter and the optical signal from the optical gate And light with In the transmission system,
When there is no electrical signal in the additional electrical buffer, the determination control circuit sets the optical gate to be transparent and simultaneously stops the operation of the optical transmitter to transmit the optical signal from the optical transmission device. When an electrical signal arrives at the additional electrical buffer before reading the header information of the optical signal from the optical transmission device received by the receiver, and until the optical signal from the optical transmission device has passed through the optical gate When the electrical signal arrives at the additional electrical buffer, the electrical signal from the optical transmission device is read out from the additional electrical buffer immediately after the optical signal is transmitted through the optical gate, and the optical gate is made non-transparent. An optical transmission system comprising: starting the operation of the optical transmitter simultaneously with setting.   The optical delay line is configured so that the determination control circuit reads the header information of the optical signal to determine transmission / non-transmission of the optical signal and delays the optical signal by a time required for performing the control. The optical transmission system according to claim 1. In an optical transmission device connected between an optical transmission device and an optical reception device,
An optical splitter for branching an optical signal from the optical transmitter; an optical receiver for receiving one of the branched optical signals; an electrical buffer for storing the signal of the optical receiver; and An additional electrical buffer for storing a signal to be added to the optical signal; reading optical signal header information received by the optical receiver to determine transmission / non-transmission of the optical signal; and from the electrical buffer and the additional electrical buffer A determination control circuit that reads the electrical signal of the optical signal, an optical transmitter that converts the electrical signal read from the determination control circuit into an optical signal and transmits the optical signal, and an optical delay that transmits the other of the branched optical signals An optical gate for transmitting / not transmitting an optical signal from the optical delay line, and an optical splitter for combining the optical signal from the optical transmitter and the optical signal from the optical gate,
When there is no electrical signal in the additional electrical buffer, the determination control circuit sets the optical gate to be transparent and simultaneously stops the operation of the optical transmitter to transmit the optical signal from the optical transmission device. When an electrical signal arrives at the additional electrical buffer before reading the header information of the optical signal from the optical transmission device received by the receiver, and until the optical signal from the optical transmission device has passed through the optical gate When the electrical signal arrives at the additional electrical buffer, the electrical signal from the optical transmission device is read out from the additional electrical buffer immediately after the optical signal is transmitted through the optical gate, and the optical gate is made non-transparent. An optical transmission apparatus characterized in that the operation of the optical transmitter is started simultaneously with the setting.   The optical delay line is configured so that the determination control circuit reads the header information of the optical signal to determine transmission / non-transmission of the optical signal and delays the optical signal by a time required for performing the control. The optical transmission device according to claim 3, wherein: In an optical transmission method of an optical transmission device connected between an optical transmission device and an optical reception device,
When there is no signal to be added to the optical signal from the optical transmitter, the optical gate for transmitting / non-transmitting the optical signal is set to be transparent, and the optical signal from the optical transmitter is transmitted to receive the optical signal. To the device,
When a signal to be added to the optical signal from the optical transmitter arrives before reading the header information of the optical signal from the optical transmitter, and the optical signal from the optical transmitter passes through the optical gate. When a signal to be added to the optical signal from the optical transmission device arrives by the time the optical signal from the optical transmission device has passed through the optical gate, An optical transmission method comprising transmitting a signal to be added to the optical receiver.

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