JP2003032189A - Optical transmitter-receiver and optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmitter-receiver that suppresses radiation optical strength when an optical transmission line from the optical transmitter- receiver is broken so as to more surely ensure the safety on work and to provide an optical transmission system. SOLUTION: The optical transmitter-receiver 100 comprising an optical transmission section 110 for converting a transmission electric signal into a transmission optical signal and an optical reception section 120 for converting a received optical signal into a received electric signal, is provided with an optical power determination circuit 130 that outputs an optical power reduction signal when the optical power of the received optical signal Pi is a prescribed determination level Pt or below and with the optical transmission section 110 that reduces the optical power of the transmitted optical signal Po on the basis of the optical power reduction signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transceiver and an optical transmission system, and more specifically, to an optical connector,
The present invention relates to an optical transmitter / receiver having an optical transmitter and an optical receiver connected to an optical fiber, and an optical transmission system using the light receiver / transmitter.

[0002]

2. Description of the Related Art The structure of an optical transmission system in an optical communication system consists of an optical transmission section for converting an electric signal into an optical signal and sending it to an optical transmission line, and an electric signal for converting an optical signal in an optical transmission line shell into an electric signal. And an optical connector for transmitting and receiving is provided between the optical transmitter and the optical receiver and the optical transmission line, especially the optical fiber. In constructing and maintaining an optical transmission system, it is necessary to attach / detach the optical connector while the optical transmitter and the optical receiver are operating. Alternatively, the optical connector may be separated due to an accident.

In such a case, the transmitted optical signal may be radiated to the outside. In particular, it has been pointed out that there is a risk that a human body may be adversely affected when the transmitted light signal is irradiated.

As one method for solving such a problem, an optical shutter is provided in the optical path of the optical connector, and the optical shutter blocks the optical path when the optical transmission line is separated from the optical connector. A transceiver is considered (for example, described in Japanese Patent Laid-Open No. 2000-131566).

[0005]

However, in the conventional optical transceiver having the optical shutter mechanism, the structure reliability of the optical shutter movable part is improved and the cost is reduced due to the complicated structure of the optical connector. Was a challenge. Also, if the optical fiber is broken instead of disconnecting the optical connector,
Since the optical shutter does not move, the transmitted optical signal may be radiated to the outside from the broken portion. The prior art does not consider breakage of the optical fiber or leakage of the transmitted optical signal from the transmitting end of the optical fiber. Furthermore, in a system having two optical transmitters / receivers connected by an optical transmission line, if one of the optical transmitters / receivers disconnects the optical connector, or if a break occurs in the middle of the optical transmission line, a normal operation is performed. The optical transceiver to which the optical connector is connected does not take appropriate measures, and there is a problem that high level optical power continues to be transmitted and light continues to leak from the optical transmission line.

The main object of the present invention is to suppress the radiation intensity of the transmitted optical signal in the work even if the optical transmission line is disconnected from the optical connector or the optical fiber is disconnected, regardless of the optical shutter mechanism. It is an object of the present invention to provide an optical transmitter / receiver and an optical transmission system capable of further ensuring the safety. Another object of the present invention is, in a system having two optical transceivers connected by an optical transmission line, when the optical connector is disconnected in one optical transceiver, the other optical transceiver responds to it. , Control the light output. And when the optical connector is properly connected again, as an optical transmission system,
It is to realize an optical transmission system that returns to normal operation properly.

[0007]

In order to achieve the above object, an optical transceiver according to the present invention comprises an optical transmitter for converting an electric signal into a transmission optical signal and an optical receiver for converting a reception optical signal into an electric signal. In the optical transmitter / receiver having a signal for determining the optical power level of the received optical signal and reducing the output optical power of the optical transmitter when the optical power of the received optical signal is less than or equal to a threshold value (hereinafter optical power The optical transmission unit includes a control unit that controls the output optical power of the optical transmission unit so that the optical transmission signal is output below a certain value by the optical power reduction signal. It is provided and configured.

In the optical transmission system of the present invention, two optical transceivers each having a light transmitting section for converting an electric signal into a transmission optical signal and an optical receiving section for converting a received optical signal into an electric signal are reciprocating optical signals. In an optical transmission system coupled by fibers, at least one of the optical transceivers is the optical transceiver of the present invention.

According to the optical transmitter / receiver of the present invention, when the optical transmission line is disconnected from the optical transmitter / receiver or the optical fiber is broken, the optical power of the received optical signal is not provided without providing a mechanical optical shutter. Becomes equal to or lower than a predetermined judgment level, and the optical power reduction signal is input to the optical transmitter. Along with this, the optical power of the transmission optical signal is reduced, so that the intensity of the transmission optical signal radiated to the outside is suppressed, and an optical transceiver in which work safety is further ensured can be realized.

Further, in the optical transmission system of the present invention,
When the two optical transceivers are both configured by the optical transceiver having the optical power determination circuit of the present invention, one optical transceiver separates the optical connector and the optical fiber, as described in the following embodiments. When there is a break in the optical fiber, the optical power of the light leakage from the optical connector of the transmitter of both optical transceivers or the break of the optical fiber is automatically kept below a certain level depending on the transmission characteristics of both optical transceivers and optical fibers. It can be suppressed.

[0011]

1 shows the configuration of an embodiment of an optical transceiver according to the present invention. The optical transceiver 100 is configured to include an optical transmitter 110 and an optical receiver 120, an optical power determination circuit 130, an optical connector 140 that couples the optical transmitter 110, the optical receiver 120, and an optical transmission line.

In the above structure, the optical power determination circuit 13
0 detects the optical power of the received optical signal input to the optical receiving unit 120 via the optical connector 140, and generates an optical power reduction signal when the optical power is below a predetermined determination level, that is, a threshold value. The optical transmission unit 110 reduces the optical power of the transmission optical signal output by the optical transmission unit 110 according to the optical power reduction signal.

FIG. 2 shows the configuration of the optical transmitter 110 of FIG. The optical transmitter 110 includes a light emitting element 111 such as a semiconductor laser diode, a monitor light receiving element 112, and a drive circuit 11.
3. The light output control circuit 114. Light emitting element 11
A bias current signal and a modulation current signal are given to 1. When a transmission electric signal is input to the drive circuit 113, a modulation current signal is output from the drive circuit 113, and the light emitting element 111 generates a transmission light signal according to the high level and the low level of the modulation current signal. The optical power (PO) of the transmitted optical signal is monitored by the monitor light receiving element 112, and the optical output control circuit 11
Reference numeral 4 adjusts the signal level of the bias current signal so that the electric signal generated by the monitor light receiving element 112 becomes constant. On the other hand, when the optical power reduction signal Pc is input, the optical output control circuit 1114 changes the signal level of the bias current signal Ib to reduce the optical power Pi of the transmission optical signal.

FIG. 3 shows the configuration of the optical receiver 120 shown in FIG. The light receiving unit 120 includes a light receiving element 121 and an identification circuit 12
2. Comprised of an average current detection circuit 123. When the received light signal Pi is input, the light receiving current signal is generated from the light receiving element 1211 according to the high level and the low level of the received light signal Pi. The identification circuit 120 amplifies the received light current signal, converts it into a received electric signal, and shapes the waveform of the received electric signal. On the other hand, the average current detection circuit 123 averages a part of the received light current signal and converts it into an optical power signal Pm having a voltage level proportional to the average optical power.

FIG. 4 shows the configuration of the optical power determination circuit 130 shown in FIG. The optical power determination circuit 130 includes a comparison / determination unit 13
1, a level generation circuit 132. The comparison / determination unit 131 compares the determination level Pt generated by the level generation circuit 132 with the optical power signal Pw, and outputs the optical power signal Pw.
When w is smaller than the determination level Pt, the optical power reduction signal Pc is output. The optical power signal Pw is input from the optical receiving unit 120, and the optical power reduction signal is output to the optical transmitting unit 110.

Next, the operation of the optical transceiver 100 shown in FIG. 1 will be described. When the received optical signal Pi is input to the optical receiver 120, the optical power determination circuit 130 does not output the optical power reduction signal Pc.
From the output optical signal at the optical power level during normal operation. On the other hand, when the optical transmission line is disconnected from the optical connector 140 or when the optical fiber which is the optical transmission line is broken, the received optical signal is not input to the optical receiving unit 120. As a result, the optical power signal is reduced in proportion to the received optical signal, so that the optical power determination circuit 130 generates the optical power reduction signal. Upon receiving this optical power reduction signal,
The optical transmitter 110 reduces the transmission light output power of the transmission light signal.

FIG. 5 shows the characteristics of the received light input power dependence of the transmitted light output power in the optical transceiver 110 shown in FIG. When the received light input power Pi is higher than the determination level Pt, the transmitted light signal is output at the light power level during normal operation. On the other hand, when the received light input power Pi is smaller than the determination level Pt, the transmitted light signal is output at the light power level which is lower than that in the normal operation. That is, the optical transceiver 100 shown in FIG.
Indicates that the optical transmission line is not connected to the optical connector 140 or the optical transmission line for receiving the optical transmission line is cut, and the received optical signal P
When i is not input, an abnormality is detected in the optical transmission line, and the transmission optical signal is operated to be reduced as compared with the normal operation. As a result, even when the opening of the optical connector 140 is opened, the radiation intensity of the transmitted optical signal is suppressed, and the safety of work can be further ensured.

FIG. 6 shows the configuration of an embodiment of the optical transmission system according to the present invention. In the optical transmission system of the present embodiment, two optical transceivers 100 and 200 having an optical transmitting unit for converting an electric signal into a transmitting optical signal and an optical receiving unit for converting a received optical signal into an electric signal are reciprocating two. In the optical transmission system, the optical transmission line 500 is composed of two optical fibers 510 and 520, and the two optical transceivers 100 and 200 are the optical transceivers of the present invention. There is. That is, the optical transmitter 2 of the optical transceiver 200
10, the optical receiver 220, the optical power determination circuit 230, and the optical connector 240 have the same configurations as the optical transmitter 110 and the optical receiver 120, the optical power determination circuit 130, and the optical connector 140 of the optical transceiver 100, respectively. The display unit 150 of the optical transmitter / receiver 100 is a display unit for displaying an operation state (optical power determination circuit 230, output state of the optical transmitter / receiver 100) of the present optical transmission system. The operation of the optical transmission system when the optical connector is detached and when the optical connector is detached and reconnected will be described with reference to the characteristic diagrams of FIGS. 7A and 7B, respectively.

FIG. 7 shows the output characteristics of the optical transmitter and the optical receiver of one embodiment of the optical transmission system according to the present invention. The characteristic of FIG. 7A shows the characteristic when the optical connector is disconnected from the normal operating state of the optical transmission system. In the figure, four areas A, B, C and D respectively show the input / output characteristics of the optical transceiver 100, the optical fiber 510, the optical transceiver 200 and the optical fiber 520.

In the characteristic (a), the graphs indicated by A and C have the same characteristic as the input / output characteristic of the optical transceiver 100 described in FIG. On the other hand, the graphs shown by B and D are the optical transmission line 50.
There are two types of input / output characteristics as shown by the solid line and the broken line, respectively, depending on whether 0 is in the connected state or the disconnected state.

The optical transceivers 100 and 200 when the optical transmission line is switched from the connected state to the disconnected state by using (a).
The transition process of the optical output level will be described. When the optical transmission line 500 is in a normal connection state with the optical transceivers 100 and 200, the transmission light output level Po1 of the optical transceiver 100 is
This is the optical power level during normal operation (see FIG. 7A).
).

On the other hand, when the optical transmission line 500 is disconnected.
In (in FIG. 7A), the transmission loss of the optical fiber 510 increases, so that the received light input level Pi2 input to the optical transceiver 200 decreases (in FIG. 7A). At this time, in the optical transmitter / receiver 200, since the received light input level Pi2 is smaller than the determination level, the optical power determination circuit 230 performs control so as to reduce the optical power level of the transmission optical signal Po2 (FIG. 7 (a)). In).

The transmission optical signal of the optical transmitter / receiver 200 is further attenuated through the optical fiber 520 in the broken state (in FIG. 7A). Since the received light input level in the optical transceiver 100 at this time is smaller than the determination level Pt, the optical power determination circuit 130 of the optical transceiver 100 also reduces the optical power level Po1 of the transmission optical signal. Control is performed (in FIG. 7A). The transmission optical signal of the optical transmitter / receiver 100 is transmitted to the optical transmitter / receiver 200 again via the optical fiber 510, but the received light input level is equal to or lower than the determination level Pt (see FIG. 7A).
).

As described above, when the optical transmission line 500 is switched from the connected state to the disconnected state, the optical transceiver 10
It is clear that 0 and 200 both come to hold the reduced optical power level. As a result, the optical transmission system according to the present embodiment has the optical connector 1 of the optical transceiver.
When the optical transmission line 500 is disconnected from 40 or 240,
Alternatively, even if the optical transmission line 500 is broken, the level of emitted light to the outside is suppressed, and work safety can be further ensured.

Further, referring to FIG. 7A, the optical transmission line 500
The transition process of the optical output level of the optical transceivers 100 and 200 when the disconnection state is switched to the connection state will be described. The optical output levels of the optical transceivers 100 and 200 when the disconnection state is switched to the connection state, for example, when the optical transmission line 500 is connected to the optical connector of the optical transceiver will be described. When the optical transmission line 500 is in the disconnection state, the transmission light output level Po1 of the optical transceiver 100 is the reduced optical power level (in FIG. 7B).

On the other hand, when the optical transmission line 500 is switched to the connected state (in FIG. 7B), the transmission loss of the optical fiber 510 becomes small, so that the received optical input to the optical transceiver 200 is input. The level Pi2 becomes large (in FIG. 7B). At this time, since the received light input level Pi2 is larger than the determination level Pt, the optical transceiver 200 controls so as to generate the transmitted optical signal at the optical power level during normal operation (see FIG. 7B). ). The transmission optical signal of the optical transmitter / receiver 200 is transmitted to the optical transmitter / receiver 100 via the optical fiber 520 at a received light input level higher than the determination level Pt. Therefore, the optical transceiver 100 generates a transmission optical signal at the optical power level during normal operation (in FIG. 7B).
The transmission optical signal Po1 of the optical transmitter / receiver 100 is transmitted to the optical transmitter / receiver 200 via the optical fiber 510 again at a received light input level higher than the determination level Pt (FIG. 7 (b)).
In,). Therefore, the optical connectors of the optical transceivers 100 and 200 are normally connected, and the optical fibers 510 and 52 are connected.
When there is no disconnection of 0, normal communication operation is performed in the loop of --- in FIG. 7B.

As described above, when the optical transmission line 500 is switched from the broken state to the connected state, the optical transceiver 10
It is clear that 0 and 200 can hold the optical power level in the normal operation in cooperation with each other. The optical transmission system according to the present embodiment is provided with optical connectors 140 and 2 of an optical transceiver.
After connecting 401 to the optical transmission line 500, the optical transceiver 10
0 and 200 can work together to restore the optical power level during normal operation.

In the above embodiment of the optical transmission system, the optical transceivers 100 and 200 both use the optical transceiver of the present invention, but the optical transceiver of the present invention is implemented only in one optical transceiver. In such a case, the connection between the optical transceiver and the transmission line of the one other than the optical transceiver of the present invention can be easily and safely used as a monitor signal for suppressing the optical output power from the optical transceiver of the present invention. It can be carried out.

[0029]

As described above, according to the present invention,
The optical power level of the transmission optical signal emitted from the optical transmitter / receiver can be controlled depending on whether the optical transmission line is connected or disconnected. As a result, irrespective of the optical shutter mechanism, if the optical transmission line is disconnected from the optical connector or if the optical fiber is broken, the emission intensity of the transmitted optical signal is suppressed to ensure work safety. The optical transceiver and the optical transmission system can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an optical transceiver according to the present invention.

FIG. 2 is a block diagram showing a circuit configuration of an optical transmitter used in an embodiment of the present invention.

FIG. 3 is a block diagram showing a circuit configuration example of an optical receiving unit used in an embodiment of the present invention.

FIG. 4 is a block diagram showing a circuit configuration of an optical power determination circuit used in an embodiment of the present invention.

FIG. 5 is a diagram showing a characteristic of a received light input power dependency of a transmitted light output power in the optical transceiver of the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an embodiment of an optical transmission system according to the present invention.

FIG. 7 is a diagram showing input / output characteristics of an optical transceiver 100, an optical fiber 510, an optical transceiver 200, and an optical fiber 520 in an embodiment of an optical transmission system according to the present invention.

[Explanation of symbols]

100, 200: Optical transceiver, 110, 210: Optical transmitter, 120, 2
20: Optical receiver, 130, 230: Optical power judgment circuit, 140, 24
0: Optical connector, 500: Optical transmission line 510, 520: Optical fiber, 111: Light emitting element 112: Monitor light receiving element 113: Drive circuit 114: Optical output control circuit 121: Light receiving element 122: Identification circuit 123: Average current detection Circuit 131: Comparison judge

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoichi Honzawa             216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Inside this Opnext Co., Ltd. (72) Inventor Katsumi Saito             180 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Standing Communication System Co., Ltd. (72) Inventor Hideki Sato             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony company Hitachi Image Information System F term (reference) 5K002 AA01 AA03 BA13 BA33 CA09                       DA04 EA03 EA05 FA01

Claims (4)

[Claims] 1. An optical transmitter / receiver comprising an optical transmission section for converting a transmission electric signal into a transmission optical signal and an optical reception section for converting a reception optical signal into a reception electric signal, wherein the optical power of the reception optical signal is predetermined. The optical power determination circuit outputs an optical power reduction signal when the optical power reduction signal is lower than the determination level, and the optical transmission unit includes an optical output control unit that reduces the optical power of the transmission optical signal by the optical power reduction signal. An optical transmitter / receiver characterized by the above. 2. The optical transceiver according to claim 1, further comprising a display section for displaying an output state of the optical power determination circuit and the optical transmission section. 3. An optical transmission system comprising an optical transmission line and a plurality of optical transceivers according to claim 1 connected through the optical transmission line. 4. Optical transmission in which two optical transceivers each having an optical transmission unit for converting an electric signal into a transmission optical signal and an optical reception unit for converting a reception optical signal into an electric signal are coupled by a reciprocating optical fiber. In the system, at least one of the two optical transceivers has an optical power determination circuit that outputs an optical power reduction signal when the optical power of the received optical signal is below a predetermined determination level, The optical transmitter / receiver, wherein the optical transmitter includes an optical output controller that reduces the optical power of the transmitted optical signal by the optical power reduction signal.