JP2716029B2 - Burst optical signal reception power measurement circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver used in, for example, an optical communication system of a passive double star system, and more particularly to a burst optical signal reception power measuring circuit for measuring optical reception power. .

[0002]

2. Description of the Related Art In an optical communication system of a passive double star system, information of a plurality of slave stations is multiplexed by an optical receiver of a master station using an optical coupler as a passive element.
The passive double-star optical communication system has a feature that the optical receiving unit of the master station can respond at high speed to the reception levels of various optical signals within the dynamic range.

FIG. 2 shows the configuration of a conventional optical receiving unit arranged on the master station side. A burst optical signal 11 as a burst-like optical signal transmitted from these slave station terminal transmission devices is received by the optical receiver on the master station side connected to the plurality of slave station terminal transmission devices in a star shape, Input to the photodiode 12. The burst optical signal 11 sent from each slave station terminal transmission device to the master station is determined by the master station in advance from the reference time for transmission to each slave station terminal transmission device so that no collision occurs between them. Are set respectively.

FIG. 3 shows an example of a format of a burst optical signal. The burst optical signal 11 is G
It is composed of T / PR (GUARD TIME) signal, CS (CONTROL SLOT) signal and UD (USER DAT) signal. Here, the GT / PR signal is a bit string of all "0" for preventing burst signal collision. The CS signal refers to various control bit strings such as a synchronization establishment bit, an address, and transmission delay time control. The UD signal is user data sent from the slave station to the master station.

The photodiode 12 having received the burst optical signal 11 performs light-current conversion and outputs a current signal 13. The current signal 13 is input to a preamplifier 14. The preamplifier 14 amplifies this and outputs it as an amplified voltage signal 15. The amplified voltage signal 15 is AOC16 and ATC17.
Is input to both. The AOC 16 is an automatic offset control circuit for generating an offset control signal 18 to be input to the preamplifier 14. The preamplifier 14 uses the offset control signal 18 to output an amplified voltage signal 15 having a constant offset.

ATC 17 is an automatic threshold control circuit,
The amplified voltage signal 15 is input, and the received data 19 identified at a predetermined threshold level is output. The received data 19 is input to a peak hold circuit 21, and a peak hold signal 22 holding the peak value of the signal is output. The peak hold signal 22 is input to the ATC 17 and controls the threshold level when the amplified voltage signal 15 is binarized. That is, the burst optical signal 11 transmitted from each slave station terminal transmission device has a reception level on the master station side due to a difference in transmission distance or a difference in light emission level of the light emitting element for each slave station terminal transmission device. Different. Therefore, the master station performs adjustment such as controlling the threshold value of the burst optical signal 11 for each slave station, so that the burst optical signal 11 sent from each slave station terminal transmission device can be stably received. Like that.

[0007]

In such an optical communication system of the passive double star system, optical burst signals transmitted by a plurality of slave terminal transmission devices are respectively branched on the transmission line by the optical branch at the master station side. ing. When adding a slave station terminal transmission device, the optical receiver on the master station measures the reception power of the optical signal sent from the slave station at the time of extension, and it must be within an acceptable level. It is necessary to confirm. As a proposal for improving the detection accuracy when the reception power is small, Japanese Patent Application Laid-Open No.
No. 29542 discloses this. As a technique for compensating for the nonlinear characteristic of the reception power, Japanese Patent Application Laid-Open No. Sho 64-7
There is one disclosed in Japanese Patent No. 4768.

[0008] Conventionally, in this type of optical communication system, an additional slave station terminal transmission device is made to continuously emit light only during the reception power measurement time, and the reception power of the optical signal is measured. This is because the optical power meter used on the master station side when receiving power is measured receives the received power for a certain time and calculates this as an average value,
This is because the reception timing is not fixed and may overlap with the burst optical signal 11 transmitted from another slave station terminal transmission device, and the level of the reception power may not be accurately measured.

That is, in the conventional burst optical signal reception power measuring circuit, when measuring the reception power of the additional slave station terminal transmission device, the operation of the existing slave station terminal transmission device is stopped. There is a problem that the existing slave station terminal transmission device cannot transmit an optical signal to the master station.

Accordingly, an object of the present invention is to provide a burst optical signal reception power capable of continuing the operation of another slave station terminal transmission device even when the added slave station terminal transmission device transmits an optical signal for measuring the reception power. It is to provide a measuring circuit.

[0011]

According to the first aspect of the present invention, (a) a burst optical signal as an optical signal generated in a burst form is sequentially and selectively input from each of the slave station terminal transmission devices to perform photoelectric conversion. Photoelectric conversion means for outputting an electrical signal
(B) Signal conversion in which an electric signal converted by the photoelectric conversion means is input, and converted into an electric signal in which the reference signal levels of these electric signals match between the slave terminal transmission devices and output. Means, (c) timing discriminating means for discriminating the timing at which the slave station terminal transmission device to be added in each slave station terminal transmission device transmits a burst optical signal, and (d) this timing discriminating means. At the determined timing, the electric signal converted by the signal converting means is input, and the reception power corresponding to the signal level of the electric signal corresponding to the burst optical signal transmitted from the slave terminal transmission device to be added is detected. The reception power detection means is provided in a burst optical signal reception power measurement circuit.

That is, according to the first aspect of the present invention, the timing at which the slave station terminal transmission apparatus to be added among the slave station terminal transmission apparatuses transmits a burst optical signal is determined by the timing determination means, and signal conversion is performed. The corresponding electric signal converted by the means is processed at this timing to detect the received power. Since the burst optical signal sent from another slave terminal transmission device is input to the photoelectric conversion means at a different timing from the burst optical signal sent from the slave terminal transmission device to be added, It is not necessary to stop the operation of the slave station terminal transmission device.

According to the second aspect of the present invention, (a) a burst optical signal as an optical signal generated in a burst form is sequentially and selectively input from each of the slave station terminal transmission devices to perform optical-current conversion to perform a current signal. And (b) the current signal converted by the light-current conversion means is input and converted into a voltage signal, and the converted voltage signal is transmitted between the slave terminal transmission devices. Signal converting means for adjusting the offset so that the reference signal levels are equal to each other, and (c) the slave station terminal transmission apparatus to be added among the slave station terminal transmission apparatuses transmits a burst optical signal. (D) a voltage signal converted by the signal converting means at the timing determined by the timing determining means, and a slave station terminal to be added To and a reception power detection means for detecting a reception power corresponding to the signal level of the voltage signal corresponding to the transmitted bursts optical signal transmission device to the burst optical signal receiving power measurement circuit.

That is, according to the second aspect of the present invention, the timing at which the slave terminal transmission device to be added among the slave terminal transmission devices transmits a burst optical signal is determined by the timing determination means, and the signal conversion is performed. The corresponding voltage signal converted by the means is processed at this timing to detect the reception power. The voltage signal to be detected is a signal obtained by adjusting the offset so that the reference signal levels of the slave terminal transmission devices match each other. Since the burst optical signal sent from another slave terminal transmission device is input to the photoelectric conversion means at a different timing from the burst optical signal sent from the slave terminal transmission device to be added, It is not necessary to stop the operation of the slave station terminal transmission device.

According to a third aspect of the present invention, in the burst optical signal reception power measuring circuit according to the first or second aspect,
The reception power detection means is characterized by outputting a reception power abnormality signal indicating that the reception power is abnormal when detecting a low-level reception power that causes reception failure. That is, when measuring the reception power of the burst optical signal sent from the slave station terminal transmission device to be added, if this is a low level that causes a failure in the signal discrimination at the time of subsequent reception. This indicates that the reception power is abnormal, so that some countermeasures can be taken.

According to a fourth aspect of the present invention, in the burst optical signal reception power measuring circuit according to the first or second aspect, the signal converting means converts the burst optical signal sent from the slave station terminal transmission device to be added. Peak holding means for holding the peak of the signal obtained by the conversion; the peak value held by the peak holding means is input to the reception power detection means to detect the reception power of the slave station terminal transmission device; It is characterized by being performed.

According to a fifth aspect of the present invention, in the burst optical signal reception power measuring circuit according to the second aspect, the burst optical signal is a binary optical signal, and the signal converting means corresponds to the signal "0" among them. It is characterized in that the offset of each voltage signal is adjusted so that the signal level matches the voltage signals corresponding to the burst optical signals transmitted from the respective slave terminal transmission devices.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows the configuration of a burst optical signal reception power measuring circuit according to an embodiment of the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Also in the circuit of the present embodiment, the burst optical signal 11 sent from each slave station terminal transmission device is input to the photodiode 12, and the current signal 13 as a result of the light-current conversion is output. The current signal 13 is input to the preamplifier 14, and the signal level on the L (low) level side of the burst optical signal 11 sent from each slave station terminal transmission device is made uniform by the offset control signal 18 supplied from the AOC 16 ( That is, the amplified voltage signal 15 with the offset being constant is output. The amplified voltage signal 15 is input to the AOC 16 and the ATC 16
17 is input.

ATC 17 is an automatic threshold control circuit,
The amplified voltage signal 15 is input, and the received data 19 identified at a predetermined threshold level is output. The received data 19 is transmitted to the peak hold circuit 21 and the TDMA control unit 3.
1 is input. The peak hold circuit 21 holds the respective peak values of the burst optical signals 11 transmitted at intervals from each slave station terminal transmission device, and sequentially outputs them as a peak hold signal 22. That is, when these burst optical signals 11 are composed of binary signals, the level of the signal H (high) is held for each slave station terminal transmission apparatus, and these signals are transmitted to the peak hold signal 2.
2 will be output. Peak hold signal 22
Are input to the ATC 17 to control a threshold level when the amplified voltage signal 15 is binarized. This is the same as the conventional circuit shown in FIG.

In the burst optical signal reception power measuring circuit of the present embodiment, the peak hold signal 22 output for each slave station terminal transmission device is also input to the received light power detection unit 32. The received light power detection unit 32 is a circuit for detecting the received light power on the master station side when the burst optical signal 11 is sent from the additional slave station terminal transmission device. The received light power detector 32 receives the timing pulse 34 sent from the TDMA controller 31 and detects the received power at that timing. Then, an optical burst signal reception power signal 35 indicating the reception power of the optical burst signal is transmitted to a monitor (not shown) for display, and when there is an abnormality in the reception power, a reception power abnormality signal 36 is output. .

That is, the burst optical signal reception power measuring circuit of this embodiment waits for the input of the timing pulse 34 in a state where each slave station terminal transmission device sequentially transmits the burst optical signal 11 as usual. . Then, when the slave station terminal transmission device to be added transmits the burst optical signal 11 for measuring the reception power in a time slot allocated in advance by the master station, the reception power detection unit 32 outputs the timing pulse 34.
The received power is detected at this input timing.
Then, the detection result is output as the optical burst signal reception power signal 35 or the reception power abnormality signal 36.

The master station provided with the burst optical signal reception power measuring circuit of the present embodiment can transmit the burst optical signals 11 to the master station without causing each of the slave station terminal transmission devices to collide. The timing is being set. In other words, the master station individually sets beforehand the delay time until each slave station terminal transmission device starts transmitting the burst optical signal 11, starting from a reference time point that occurs in a certain cycle. Regarding the slave station terminal transmission device to be added, the master station measures the time required for signal transmission with the slave station terminal transmission device before starting measurement of the reception power. Then, based on this, a delay time starting from a reference time is determined so that the burst optical signals 11 transmitted from the other slave station terminal transmission devices at different times do not collide. When measuring the reception power, the master station notifies the determined delay time to the extension-target slave station terminal transmission apparatus in advance.

Therefore, the slave station terminal transmission device to be added has its own burst optical signal 1 for this delay time.
1 will be delayed. TDMA control unit 31
Measures the delay time allocated to the slave station terminal transmission device to be added, starting from the reference time point. Then, when this delay time has elapsed, a timing pulse 34 is sent to the received light power detection unit 32.

When the timing pulse 34 is input, the received light power detector 32 measures the received power for the reception time of the burst optical signal 11 allocated to the slave station terminal transmission device to be added. Such time setting can be realized by counting a reference clock (not shown) from the input time point of the timing pulse 34 until reaching a predetermined count value. Of course, it is possible to set the time for measuring the reception power even by using a normal timer circuit or a one-shot multivibrator.

When the received light power is measured for the above-described reception time, the received light power detector 32 averages the result. Then, the average value of the received power is compared with a predetermined reference level. This reference level is set to a minimum required reception level in a system for communicating the burst optical signal 11. As a result of this comparison, if a very small reception power that does not reach the reference level is detected,
The reception power abnormality signal 36 is output. In this case,
There is a possibility that there is some abnormality in the transmission line connecting the slave station terminal transmission device and the master station, or that the light emitting element such as a semiconductor laser of the slave station terminal transmission device or a peripheral circuit for driving the same is defective. Therefore, in this case, the slave station terminal transmission device to be added is to be repaired.

In other cases, the received light power detector 3
2 outputs an optical burst signal reception power signal 35 representing the reception power and displays it on the monitor. Depending on the device, even when the reception power abnormality signal 36 is output, the optical burst signal reception power signal 35 may be output and displayed on a monitor (not shown).

[0029]

As described above, claims 1 to 5 are provided.
According to the described invention, utilizing the fact that each slave station terminal transmission device transmits a burst optical signal to the master station in a time-division manner,
The timing discriminating means judges the timing at which the slave station terminal transmission device as an extension target transmits a burst optical signal, and measures the reception power of the burst optical signal at this timing. For this reason, the other slave station terminal transmission device can transmit the burst optical signal as usual even while measuring the reception power of the burst optical signal for the new slave station terminal transmission device. Therefore, there is no need to stop the operation of the system when adding a slave station. Further, even in the existing slave station terminal transmission device, it is possible to arbitrarily check the reception power of these burst optical signals, and there is an advantage that the maintenance and inspection thereof are facilitated.

[Brief description of the drawings]

FIG. 1 is a block diagram of a burst optical signal reception power measuring circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a conventional optical receiving unit arranged on a master station side.

FIG. 3 is a format configuration diagram illustrating an example of a format of a burst optical signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Burst optical signal 12 Photodiode 14 Preamplifier 16 AOC 17 ATC 19 Received data 21 Peak hold circuit 31 TDMA control unit 32 Reception power detection unit 36 Reception power abnormal signal

Claims (5)

(57) [Claims] 1. A photoelectric conversion means for sequentially inputting a burst optical signal as an optical signal generated in a burst form from each of the local station terminal transmission devices, performing photoelectric conversion and outputting an electric signal, and the photoelectric conversion means. Signal converting means for inputting the electric signal converted by the means, converting the electric signal into a signal having a signal level which is the same as a reference of these electric signals between the slave station terminal transmission apparatuses, and outputting the electric signal; Timing discriminating means for discriminating the timing at which the slave station terminal transmitting device as an extension target in the terminal transmitting device transmits a burst optical signal; and the signal converting unit converts the signal at the timing discriminated by the timing discriminating device. Input the electric signal after,
Receiving power detecting means for detecting a receiving power corresponding to a signal level of an electric signal corresponding to a burst optical signal transmitted from a slave terminal transmission apparatus to be added. circuit. 2. An optical-current converting means for inputting a burst optical signal as an optical signal generated in a burst form sequentially from each of the terminal transmission devices and performing optical-current conversion and outputting a current signal. The current signal converted by the light-current conversion means is input and converted into a voltage signal, and the slave station terminal transmission devices are configured to match the reference signal levels of the converted voltage signals with each other. Signal conversion means for adjusting the offset; timing discrimination means for discriminating the timing at which a slave station terminal transmission device to be added in each slave station terminal transmission device transmits a burst optical signal; At the determined timing, the voltage signal converted by the signal conversion means is input,
Receiving power detecting means for detecting a receiving power corresponding to a signal level of a voltage signal corresponding to a burst optical signal transmitted by the slave station terminal transmission apparatus as an extension target. circuit. 3. The reception power detection means outputs a reception power abnormality signal indicating that the reception power is abnormal when detecting a low-level reception power that causes a failure in reception. 3. The burst optical signal reception power measuring circuit according to claim 1 or 2. 4. A peak hold means for holding a peak of a signal obtained by the signal conversion means converting a burst optical signal sent from a slave station terminal transmission device as an expansion target, the peak hold means comprising: 3. The burst optical signal reception power measuring circuit according to claim 1, wherein the peak value held by the sub-station is input to reception power detection means, and the reception power of the slave station terminal transmission device is detected. . 5. The burst optical signal is a binary optical signal, and the signal conversion means converts a signal level corresponding to the signal “0” into a burst optical signal transmitted from each of the slave station terminal transmission devices. 3. The circuit according to claim 2, wherein the offset of each voltage signal is adjusted so that the corresponding voltage signals match each other.