JP2003324392A - Equipment and system for bidirectional optical communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize with a simple circuit a situation that data is transmitted by returning light transmitted from the opposite party to the opposite party while omitting a light emitting element. <P>SOLUTION: A center device 11 and a remote device 12 are connected by an optical fiber 13 for an outgoing signal and an optical fiber 14 for an incoming signal, and as for light on the optical fiber for an incoming signal, light transmitted on the optical fiber for an outgoing signal is returned (branched) for use. In this configuration, the remote device allocates incoming data only to '1' of an outgoing optical signal, returns the incoming data as it is without attenuating light when the outgoing signal is '1' and attenuates light to return the light when the outgoing signal is '0'. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional optical communication device and a bidirectional optical communication system for omitting a light emitting element and returning light transmitted from a partner side to the partner side to transmit data. FTTH (Fiber-To-The-Hom
e) Two-way optical communication device and two-way optical communication system suitable for system.

[0002]

2. Description of the Related Art FIG. 9 shows an optical communication system for performing bidirectional communication between a center device 91 and a remote device 92. The center device 91 and the remote device 92 have an electro-optical converter (E → O) 93, 96 and an opto-electric converter (O → O), respectively.
E) 94 and 95 are provided, and the center device 91 and the remote device 92 are connected by the downstream signal optical fiber 13 and the upstream signal optical fiber 14. The downlink transmission data from the center device 91 is converted into an optical signal by the electro-optic converter 93, and the remote device 9 is passed through the downlink signal optical fiber 13.
In addition to 2, it is converted into an electric signal by the optical-electrical converter 95 and becomes downlink reception data. The reverse is done in the up direction. In the example of FIG. 9, two optical fibers are used, but the number of optical fibers may be one, such as different optical wavelengths for upstream and downstream.

However, in general, the electro-optical converter 9
A laser diode (LD) is used as the light source of Nos. 3 and 96, but there is a problem that the LD is difficult to handle such as temperature control and output level control.

Therefore, as a conventional example (1) in which the light emitting element on one device side of the bidirectional optical communication system is omitted, for example, Japanese Patent Application Laid-Open No. 62-155632 discloses a system using one optical fiber. Utilizing the fact that the downlink optical power is higher than the uplink optical power and the downlink and uplink signal forms and transfer rates are different, a method has been proposed in which the downlink light is branched on the device side receiving the downlink light and used as the uplink light. ing. Further, as another conventional example (2), for example, Japanese Unexamined Patent Publication No.
Japanese Patent No. 130062 discloses a method of using different downlink / uplink modulation frequencies or the like when a device that receives downlink light branches the downlink light and uses it as upstream light in a system using two optical fibers. Is proposed.

Further, as still another conventional example (3), for example, Japanese Patent Laid-Open No. 5-41694 discloses a system in which a master station and a plurality of slave units are connected via one loop-shaped optical fiber. There has been proposed a method of omitting the light emitting element of the slave unit by turning on / off the transmission light from the master station according to the transmission data.

[0006]

However, each of the above conventional examples has a problem that the circuit configuration becomes complicated.

In view of the above-mentioned problems of the conventional example, the present invention can be realized by a simple circuit when omitting the light emitting element and returning the light transmitted from the other party to the other party and transmitting the data. It is an object of the present invention to provide a bidirectional optical communication device and a bidirectional optical communication system capable of performing the above.

[0008]

In order to achieve the above object, a two-way optical communication device of the present invention returns light transmitted from a partner side to the partner side and transmits data. In the above configuration, a means for encoding and transmitting the transmission data by controlling the power of the light reflected back to the other side according to the value of the transmission data being "1" or "0" is provided. . With the above structure, when a light emitting element is omitted and light transmitted from the other party is returned to the other party to transmit data, it can be realized by a simple circuit.

According to the present invention, in the bidirectional optical communication device according to claim 1, 1 bit of the transmission data is assigned to a 1-bit section of the reception data transmitted from the other party, and the value of the transmission data is " In the case of "1", the light transmitted from the other party is returned to the other party without being attenuated in the 1-bit section, and when the value of the transmission data is "0", the light transmitted from the other party. Is attenuated in the 1-bit section and is returned to the other side to encode and transmit the transmission data. The present invention also
The two-way optical communication device for receiving the light returned by the two-way optical communication device according to claim 2, wherein the delay means delays the transmission data so that the transmission data and the reception data of the returned light have the same timing. When the value of the transmission data delayed by the delay unit is "1", the reflected light is referred to, and when it is returned as it is without being attenuated, the value of the reception data is determined to be "1". However, when it is attenuated and folded back, a means for judging that the value of the received data is “0” and decoding it is provided.

According to the present invention, in the bidirectional optical communication device according to claim 1, 1 bit of the transmission data is assigned to a bit block of the reception data transmitted from the partner side, and the value of the transmission data is "1". In this case, the light transmitted from the other party is returned to the other party without being attenuated by the bit block, and when the value of the transmission data is “0”, the light transmitted from the other party is The feature is that the transmission data is encoded and transmitted by attenuating the bit block and returning it to the other side.
The present invention also provides a bidirectional optical communication device for receiving the light returned by the bidirectional optical communication device according to claim 4,
The transmission data is always transmitted for each bit block having a fixed number of bits including "1" of 1 bit or more, and the block detection means for detecting the division of the bit block from the folded light, and the division from the block detection means. Based on the timing, the reflected light is referred to, and when the light is returned as it is without being attenuated in at least one bit section in the bit block, it is determined that the value of the received data is “1”, and And a means for judging that the value of the received data is "0" and decoding when the value is attenuated and returned in the bit section.

The bidirectional optical communication system of the present invention is configured to perform bidirectional optical communication between the bidirectional optical communication device according to claim 2 and the bidirectional optical communication device according to claim 3. The bidirectional optical communication system of the present invention is configured to perform bidirectional optical communication between the bidirectional optical communication device according to claim 4 and the bidirectional optical communication device according to claim 5.

The present invention also provides a bidirectional optical communication device according to claim 2 or 4 as a first communication device, and claims 3 or 5
In the two-way optical communication system for performing two-way optical communication with the first and second communication devices, the two-way optical communication device according to claim 2 as a second communication device, the first communication device is started up. Afterward, or for a certain period of time after receiving an instruction from the second communication device, the light transmitted from the second communication device is returned to the second communication device as it is, and the second communication device The data sent to the first communication device is compared with the data sent back from the first communication device to detect the round trip time from the transmission data to the reception data, and the reception data is detected based on the round trip time. Is decoded.

The present invention also provides the bidirectional optical communication device according to claim 2 or 4 as the first communication device, and claims 3 or 5
In the two-way optical communication system for performing two-way optical communication with the first and second communication devices, the two-way optical communication device according to item 2 is used as a second communication device. The bit pattern is included in the transmission data and transmitted to the first communication device, and the optical signal received by the first communication device from the second communication device is sent back to the second communication device. The second communication device detects the position of the bit pattern to detect the round trip time from the transmission data to the reception data, and decodes the reception data based on the round trip time.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is a block diagram showing an embodiment of a bidirectional optical communication device and a bidirectional optical communication system according to the present invention, and FIG. 2 is an explanatory diagram showing a relationship between downlink data and uplink data. 3 is a block diagram showing the remote device of FIG. 1 in detail, and FIG. 4 is a block diagram showing the center device of FIG. 1 in detail.

In the system shown in FIG. 1, the center device 1
1 and the remote device 12 are connected by a downstream signal optical fiber 13 and an upstream signal optical fiber 14, and the light transmitted on the downstream signal optical fiber 13 is returned to the light on the upstream signal optical fiber 14. Used (branched).

Here, the signals on the optical fibers 13 and 14 are set to a strong level for the value "1" and a weak level for the value "0". For example, the signal on the downstream signal optical fiber 13 is shown in FIG.
It is assumed that it is "1001011 ..." As in (a).
On the other hand, it is assumed that the upstream data is “1001 ...”. The remote device 12 partially folds back the downstream optical signal. At this time, paying attention to the fact that the downstream optical signal is "1", and allocates upstream data only to the downstream optical signal "1". That is, when the upstream data is "1", it is returned as it is,
When it is "0", the light is attenuated and then folded back. In this example,
The upstream signal is as shown in FIG.

The center device 11 can discriminate the upstream data by comparing the upstream signal with the downstream signal. In this method, the speed of the upstream signal changes depending on the ratio of "1" of the downstream data, but generally, the downstream signal is scrambled so that the mark rate is 0.5.
In many cases, the upstream signal speed is about half of the downstream signal speed. Here, in order for the center device 11 to discriminate the upstream data by comparing the upstream signal and the downstream signal, the time until the light output from the center device 11 returns (hereinafter referred to as "round trip time").
However, the method will be described later.

FIG. 3 shows the configuration of the remote device 12. The optical branching device 31 divides the downstream optical signal transmitted on the downstream signal optical fiber 13 into two, and divides the optical signal into an optical-electrical converter (O-
E) 32 and the optical attenuator 33 (ATT). The optical-electrical converter 32 regenerates downlink received data from the downlink optical signal branched by the optical branching device 31. The optical attenuator 33 inputs the downstream optical signal branched by the optical splitter 31, and outputs it to the upstream signal optical fiber 14.

At this time, the amount of attenuation of the optical attenuator 33 is controlled by the output signal of the encoding circuit (ENC) 34, and becomes "no attenuation" at the H level and "greatly attenuates" at the L level. The encoding circuit 34 refers to the downlink reception data, fetches the uplink transmission data by 1 bit (bit) every time it is "1",
When it is "1", the control signal to the optical attenuator 33 is set to H level = no attenuation, and when it is "0", L level is set to large attenuation. As a result, it is possible to output the upstream signal as shown in FIG.

FIG. 4 shows the configuration of the center device 11. The electro-optical converter (EO) 41 converts the downlink transmission data into a downlink optical signal and outputs the downlink optical signal to the downlink signal optical fiber 13.
This is the only light source in the system. Optical-electrical converter 42
Converts the optical signal from the upstream signal optical fiber 14 into an electric signal and outputs the electric signal to the data synchronization circuit (Sync) 43 and the data demodulation circuit (DEC) 44. The data synchronization circuit 43 delays the downlink transmission data and outputs the downlink delay data matched with the timing of the uplink signal to output the data demodulation circuit 44.
Output to.

The data demodulation circuit 44 compares the downstream delay data with the output of the optical-electrical converter 42 to reproduce the upstream reception data. The reproduction of the upstream reception data in the data demodulation circuit 44 is performed as follows. When the downlink delay data is "1", the uplink signal is checked. If it is H level, it is determined that the upstream bit is "1", and if it is L level, it is determined that it is "0". In this way, a bidirectional optical communication system can be realized with only one light source of the center device 11.

<Second Embodiment> Similarly, the signal on the optical fiber is set to a strong level for the value "1" and a weak level for the value "0". Here, the downlink data is encoded by the 8B / 10B coding rule, and an example of conversion of this coding rule is shown in FIG.
When the downlink transmission data is “4B, 7F, E9, ...” (Hexadecimal), the downlink optical signal is as shown in FIG. On the other hand, it is assumed that the upstream data is “1001 ...”. The remote device 12 partially returns the downstream optical signal,
At this time, uplink data is allocated for each 10-bit code.
That is, when the upstream data is "1", it is returned as it is, and when it is "0", the light is attenuated and then returned. In the case of this example, the upstream signal is as shown in FIG.

The center device 11 can discriminate the upstream data by comparing the upstream signal with the downstream signal. In this method, 1/8 of the downlink data rate becomes the uplink data rate. Therefore, it is suitable for an application in which an up speed is not so required as compared with a down speed. At this time as well, the center device 11 needs to know the round trip time, which method will be described later.

FIG. 7 shows the configuration of the remote device 12. The optical branching device 31 divides the downstream optical signal transmitted on the downstream signal optical fiber 13 into two, and divides the optical signal into an optical-electrical converter (O-
E) Output to 32 and optical attenuator 33. Optical-electrical converter 3
Reference numeral 2 reproduces downlink reception data from the downlink optical signal branched by the optical branching device 31, and outputs it to the 10B-8B conversion circuit 76 and the delimiter detection circuit (BNDY) 74. 10B-8B
The conversion circuit 76 restores the 10-bit encoded downlink data to the original 8-bit data.

The delimiter detection circuit 74 is an opto-electric converter 32.
The 10-bit signal delimiter is detected from the output of and the notifying circuit 75 is notified of this. As shown in FIG. 6A, the encoding circuit 75 fetches 1 bit of upstream transmission data for each 10-bit signal division, and if it is "1", the optical attenuator 3
The control signal to 3 is set to H level = no attenuation, and when it is "0", L level = large attenuation. As a result,
The uplink transmission signal as shown in (b) can be output.

FIG. 8 shows the structure of the center device. Electricity-
The optical converter (EO) 41 converts the downlink transmission data into a downlink optical signal and outputs it to the downlink signal optical fiber 13. This is the only light source in the system. The optical-electrical converter 42 converts the optical signal from the upstream signal optical fiber 14 into an electric signal and outputs the electric signal to the data synchronization circuit (D-Sync) 83 and the data demodulation circuit (DEC) 84. The data synchronization circuit 83 obtains the time difference between the downlink transmission data and the uplink reception signal, and outputs a timing signal indicating the 10-bit code delimiter of the uplink signal to the data demodulation circuit 84. The data demodulation circuit 84 inspects the output of the opto-electric converter 42 based on it, and
If the bit code continues to be at the L level, it is determined that the upstream bit is "0", and even if 1 bit of the 10-bit code period is at the H level, the upstream bit is "1". To determine.

In this way, an optical communication system can be realized with only one light source of the center device. In the previous example, it was necessary to measure the round trip time, but in this example, since it is sufficient to know the 10-bit signal delimiter in the upstream signal, the delimiter timing is detected only from the upstream signal without looking at the downlink transmission data. You may do it.

Next, a method of knowing the round trip time will be described. In the optical communication method described above, the remote device 12 processes the downlink signal and sends it back, so that the center device 11 needs to know how much the signal transmitted by itself is delayed and returned. is there.
Two methods for solving it will be described.

(1-1) The remote device 12 simply loops back the downlink signal for a certain period of time after starting up without adding data to the upstream optical signal. When the remote device 12 is not connected, or when the remote device 12 is connected but is not started up and is not performing the loopback operation, there is no upstream signal when viewed from the center device 11. After that, when the remote device 12 starts up, the center device 11 receives the upstream signal, but since the remote device 12 performs only the return operation, the downstream signal is detected as it is. Therefore, the round trip time can be known by comparing the patterns of the transmission data and the reception data. This method is effective in a case where a remote device 12 is newly connected in a system in which information is continuously transmitted from the center device 11 to a plurality of remote devices 12 such as broadcasting.

(1-2) When the remote device 12 receives the upstream transmission stop instruction from the center device 11, it simply returns the downstream signal without carrying the upstream data for a certain period of time. Not only user data but also a remote control signal is superimposed on the downlink transmission signal. A round trip time can be measured by instructing to stop transmission by the control signal. This method is more complicated than the method of (1), but since it can be measured at any time, for example, when a transmission error occurs in uplink data, it is possible to confirm whether it is due to fluctuations in round trip time. It has the advantage of being easy.

(2) The center device 11 has a predetermined bit pattern A at regular time intervals (for example, 1 s).
To send. The transmission cycle of the bit pattern A is set sufficiently larger than the expected round trip time. When transmitting the bit pattern A, even when the normal downlink data is being transmitted, at the relevant timing, the bit pattern A is interrupted and transmitted.

The remote device 12 always has the bit pattern A.
Is monitored, and the bit pattern A is output when the downlink data is reproduced. It can be considered that frame synchronization is established by the frame synchronization pattern A for a frame having a cycle of 1 s. Therefore, if the synchronization is established, it is possible to obtain the downlink received data in which the bit pattern A is surely removed, and even if the same bit pattern as the bit pattern A exists in the downlink received data, it is erroneously deleted. There is no end.

Further, the center device 11 monitors the upstream signal returned by the remote device 12 and measures the time from the transmission of the bit pattern A to the return of the bit pattern A to determine the round trip time. I can know. However, if there is the same bit pattern as the bit pattern A in the upstream data, an erroneous result will be produced, so that the center device 11 also needs a function for frame synchronization. The bit pattern A
It is also possible to apply a general frame synchronization technique, such as determining a bit pattern B different from the above and transmitting the bit patterns A and B alternately to reduce the possibility of erroneous synchronization.

[0034]

As described above, according to the present invention, when a light emitting element is omitted and light transmitted from the other party is returned to the other party and data is transmitted, it can be realized by a simple circuit. You can In addition, the remote device is often placed in the home of a general user, and the merit of simply configuring the remote device is great.

[Brief description of drawings]

FIG. 1 is a system configuration diagram according to a first embodiment of the present invention.

FIG. 2A is a diagram showing an example of a downlink signal. (B) is a figure which shows the example of the upstream signal which added the upstream data.

FIG. 3 is a block diagram showing the remote device of FIG. 1 in detail.

4 is a configuration diagram showing in detail the center device of FIG.

FIG. 5 is an 8B-10 according to the second embodiment of the present invention.
Explanatory drawing showing B coding rule

FIG. 6A is an explanatory diagram showing an example of downlink data according to the second embodiment of the present invention. FIG. 6B is an explanatory diagram showing an example of uplink data according to the second embodiment of the present invention.

FIG. 7 is a block diagram showing in detail a remote device according to a second embodiment of the present invention.

FIG. 8 is a block diagram showing in detail a center device according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional optical communication system.

[Explanation of symbols]

11 Center device 12 Remote device 13 Optical fiber for downstream signal 14 Upstream optical fiber 31 Optical switch 32, 42 optical-electrical converter 33 Optical attenuator 34, 75 encoding circuit 41 Electric-optical converter 43,83 data synchronization circuit 44, 84 data demodulation circuit 74 Break detection circuit

Claims (13)

[Claims] 1. A two-way optical communication device that transmits data by returning light transmitted from a partner side to the partner side, and the partner side according to the value of transmission data being "1" or "0". A two-way optical communication device comprising means for encoding and transmitting transmission data by controlling the power of the light reflected back to the. 2. One bit of transmission data is assigned to a one-bit section of reception data transmitted from the other side,
When the value of the transmission data is "1", the light transmitted from the other party is returned to the other party without being attenuated in the 1-bit section, and when the value of the transmission data is "0", the other party The bidirectional optical communication device according to claim 1, wherein the light transmitted from the optical fiber is attenuated in the 1-bit section and is returned to the other side to encode the transmission data for transmission. 3. A bidirectional optical communication device for receiving the light reflected by the bidirectional optical communication device according to claim 2, wherein the transmission data has the same timing as the reception data of the folded light. And a value of the transmission data delayed by the delay unit is "1".
In this case, the value of the received data is judged to be "1" when the light is returned as it is without being attenuated, and the value of the received data is "0" when it is attenuated and returned. And a means for determining and decoding the two-way optical communication device. 4. One bit of transmission data is assigned to a bit block of reception data transmitted from the other party, and when the value of the transmission data is “1”, the light transmitted from the other party is assigned to the bit. It returns to the other party as it is without being attenuated by the block, and the value of the transmission data is "0".
In this case, the transmission data is encoded and transmitted by attenuating the bit block of the light transmitted from the other party and returning it to the other party.
The two-way optical communication device according to. 5. A bidirectional optical communication device for receiving the light returned by the bidirectional optical communication device according to claim 4, wherein the transmission data always has a fixed number of bits including “1” of 1 bit or more. Transmitting for each bit block, from the folded light, block detection means for detecting a bit block break, based on the break timing from the block detection means,
With reference to the returned light, when the light is returned as it is without being attenuated in at least one bit section in the bit block, the value of the received data is “1”.
And a means for judging that the value of the received data is “0” when it is attenuated and returned in the entire bit section and decoding the value, the two-way optical communication device. 6. A bidirectional optical communication system, wherein bidirectional optical communication is performed between the bidirectional optical communication device according to claim 2 and the bidirectional optical communication device according to claim 3. 7. A bidirectional optical communication system, wherein bidirectional optical communication is performed between the bidirectional optical communication device according to claim 4 and the bidirectional optical communication device according to claim 5. 8. The bidirectional optical communication device according to claim 2 or 4 is a first communication device, and the bidirectional optical communication device according to claim 3 or 5 is a second communication device. In a two-way optical communication system for performing two-way optical communication with a second communication device, a fixed time after the first communication device is started up or after receiving an instruction from the second communication device. , The light transmitted from the second communication device is returned to the second communication device as it is, and the data transmitted to the first communication device by the second communication device and the data transmitted back from the first communication device A two-way optical communication system characterized by detecting the round trip time from the transmission data to the reception data by comparing the received data and decoding the reception data based on the round trip time. 9. The bidirectional optical communication device according to claim 2 or 4 is a first communication device, and the bidirectional optical communication device according to claim 3 or 5 is a second communication device. The first communication device in a two-way optical communication system that performs two-way optical communication with a second communication device, the device being started up or receiving an instruction from the second communication device. A two-way optical communication device comprising means for returning the light transmitted from the second communication device to the second communication device as it is for a certain time thereafter. 10. The bidirectional optical communication device according to claim 2 or 4 as a first communication device, and the bidirectional optical communication device according to claim 3 or 5 as a second communication device. Second
A second communication device in a two-way optical communication system that performs two-way optical communication with another communication device, the data being sent to the first communication device and sent back from the first communication device. The data that was compared is compared to detect the round trip time from the transmitted data to the received data,
A two-way optical communication device comprising means for decoding received data based on this round trip time. 11. The bidirectional optical communication device according to claim 2 or 4 is a first communication device, and the bidirectional optical communication device according to claim 3 or 5 is a second communication device. Second
In the two-way optical communication system for performing two-way optical communication with the communication device, the second communication device includes a predetermined bit pattern in transmission data and transmits the transmission data to the first communication device, The first communication device sends back the optical signal received from the second communication device to the second communication device, and the second communication device detects the position of the bit pattern to detect the transmission data to the reception data. A two-way optical communication system, which detects a round trip time and decodes received data based on the round trip time. 12. The bidirectional optical communication device according to claim 2 or 4 is used as a first communication device, and the bidirectional optical communication device according to claim 3 or 5 is used as a second communication device. Second
A first communication device in a two-way optical communication system for performing two-way optical communication with another communication device, wherein the second communication device includes a predetermined bit pattern in transmission data. When sent to the communication device of 1,
A two-way optical communication device comprising means for returning an optical signal received from the second communication device to the second communication device. 13. The bidirectional optical communication device according to claim 2 or 4 as a first communication device, and the bidirectional optical communication device according to claim 3 or 5 as a second communication device. Second
A second communication device in a two-way optical communication system for performing two-way optical communication with another communication device, wherein a predetermined bit pattern is included in transmission data and transmitted to the first communication device. A means for detecting the position of the bit pattern to detect the round trip time from the transmission data to the reception data when the first communication device sends back, and decoding the reception data based on the round trip time. Two-way optical communication device equipped with.