JPH011348A - Transmitting/receiving device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmitting/receiving device with a collision detection function based on the C3MA/CD (carrier sensing multiple access/collision detection) system.

[Conventional technology]

Figure 6 shows, for example, the patent application filed in 1986 by the inventors of the present invention.
2 shows a conventional CSMA/CD type optical transmitting/receiving device shown in the specification of No. 2070. In FIG. 6, 1 is a signal input terminal for packet transmission data, 2 is a dipulse encoding circuit, 3 is an LED driver, 4 is an LED (light emitting element), 5a, 5b.

5c, 5d, 5e, 5f, 6c, 6d, 7c, and 7d are optical fibers, 8a, 8b are optical connectors, 9a, 9b are splice points, 10 is a star coupler, 1) is an APD (light receiving element), 12 is a preamplifier , 13 is a partial response (L-1) filter (hereinafter abbreviated as PR (L-1) filter), 14 is a signal discriminator, 24 is a collision detection circuit,
25 is a data reproduction output terminal, 26 is a collision detection pulse output terminal, 27 is a timing extraction circuit, 28 is a block synchronization circuit, 29 is a level detection circuit, 30 is a specified voltage input terminal, 31 is a threshold voltage generation circuit, 32 is a carrier It is off circuit.

FIG. 7 is an output waveform diagram of the PR (1, -1) filter 13. In the figure, 13a is the PR (
1, -1) filter output, 13b is the PR (1, -1) filter output on the high light reception level side, 15a is the threshold voltage on the low light reception level side, and 15b is the threshold voltage on the high light reception level side.

FIG. 8 is a diagram showing the signal collision detection level difference and threshold voltage versus received light power characteristics.

Next, the operation will be explained. The transmission signal input to signal input terminal 1 in FIG. 6 is 4 as shown in the signal series in Table 1.
It is represented by two 2-bit patterns. The dipulse encoding circuit 2 converts the signal sequences shown in Table 1 into corresponding dipulse sequences.

Table 1 Sign rule dipulse conversion refers to converting 1-bit data to 2-bit data (O→10, 1→01). LED
The driver 3 converts the dipulse series into a current, drives the LED 4, and causes the LED 4 to output a light output corresponding to the dipulse series.

The output of the LED 4 is output to an optical fiber 5a, and the optical fiber 5a is connected to optical fibers 5b and 5C by an optical connector 8a and a splice point 9a.

The optical signal outputted from the optical fiber 5C is distributed almost equally to the plurality of optical fibers 5d, 6d, and 7d by the star coupler 10 and outputted. Another optical fiber 6c input to the star coupler 10.

Similarly, the optical signal input from 7c is transmitted through multiple optical fibers 5.
It is distributed almost equally to d, 6d and 7d and output.

The optical signal input to the optical fiber 5d is connected to the splice point 9
b. It is connected to optical fibers 5e and 5f by an optical connector 8b, and the output signal of the optical fiber 5f is output to APD II. APDll converts the optical signal power into a current signal corresponding to the power and outputs it to the preamplifier 12. The preamplifier 12 converts the output current signal of APDII into a voltage signal, amplifies it, and outputs it. The preamplifier 12 outputs a voltage signal corresponding to the dipulse series shown in Table 1, which is slightly distorted due to transmission.

The PR (1, -1) filter 13 is a filter that delays the input signal by the bit period T of the da f pulse sequence (2 bit periods of the signal sequence in Table 1) and then subtracts it from the input signal at that point. be.

The output of the PR(1,-1) filter 13 has the waveform shown in Table 1. In Table 1, "x" indicates dependence on the previous preceding signal. “-” is the subtraction of 0 and 1, “
+” is the subtraction of 1 and O, “0” is the subtraction of 0 and O,
0 occurs when subtracting 1 and 1. "0'" includes more shot noise generated in APDII due to the optical signal than "0".

The signal discriminator 14 is output from the threshold voltage generation circuit 31. The threshold voltage of -Δ, which is slightly lower than the O level generated at the output of the PR(1,-1) filter 13, and the PR(1,-1)
1) Compare the outputs of the filter 13 and output the comparison result as a binary signal. Although the output of the signal discriminator 14 is slightly distorted, a discrimination output corresponding to the PR(1,-1) filter output is obtained as shown in Table 1. If optical fiber 6c
Alternatively, the optical signal (
If a collision signal (hereinafter referred to as a collision signal) is input to the star coupler 10, PR (1, -1) is input in the same manner as described above.
In the output of the signal discriminator 14, which is output from the filter I3, the discrimination results for the "0" and "0°" level signals closest to the threshold voltage are likely to be affected by the collision signal. Table 1 shows the 3rd generation where “0” and “06” occur.
It shows the output (CRV) where the bits are changed by the collision signal and the sign rule is disturbed. The collision detection circuit 24 removes distortion from the distorted output of the signal discriminator 14 using a timing signal with a period T obtained from a timing extraction circuit 27, and removes distortion from the output of the signal discriminator 14 with a period 2T obtained from a block synchronization circuit 28. The second identification output in Table 1
．． The fourth bit is sampled and the reproduced output shown in Table 1 is outputted to the data reproduction output terminal 25 as received data. In addition, the pattern of the preceding three bits from the fourth bit of the identification output in Table 1 is monitored, and when the identification output matches the CRV pattern shown in Table 1, a collision is detected at the collision detection pulse output terminal 26 as a collision has occurred. Outputs pulses. However, until the block synchronization pull-in ends at the beginning of the packet,
The detection pulse is not emitted. Of the CRv shown in Table 1, “
Since the 0 level of the third bit of the PR (1, -1) filter output is close to the threshold voltage,
Even if a minute level collision signal is added, a CRV pattern is likely to occur.Also, at the 0 level, even if the received signal level changes, the distance from the threshold voltage -Δ does not change in principle, so it operates atonally. However, among the CRVs shown in Table 1, "X100" contains a lot of shot noise in the 3rd bit 0, so it is easy to output CRV even when there is no collision, so even if this pattern is detected, there will be no collision. It is not determined that

Next, the level of the signal at which collision should be detected will be described. Second
The table shows an example of an optical level diagram of an optical local area network according to the CS MA/CD access control scheme.

In Table 2, the fiber incident power is the peak optical power coupled from the LED 4 to the optical fiber 5a in FIG. 4. The fibers are 5a, 5b, 5c in FIG.
Indicates the total length of 5d, 5e and 5f, from 0 to l Iua
It is assumed that the length is long. Fiber loss varies between 0 and 3.5 dB depending on length.

Table 2 Optical Level Diagram 100 Port star coupler refers to the star coupler 10 shown in FIG. 6, which has 100 input optical fibers and 100 output optical fibers. The loss of the 100 boat star coupler is defined by the amount of signal attenuation between the two fibers. Different fibers have different attenuation amounts, which are usually in the box range of 24.0 dB to 26.5 dB. Optical connectors and splice connections are each 0.
This assumes a score of 2 and 0 to 8 points. The connection loss per piece was 0.7 dB and 0.16 dB, respectively. The light receiving level range in which the code error rate of the reproduced output at the receiver is IQ-10 or less is -45,0 dBm to -34
,0dBm (peak value). The signal collision detection level difference refers to the level difference between the main signal and the collision signal at which the CRV detection pulse generation rate becomes equal to or higher than a specified value at the time of a collision. The system margin indicates the difference between the actually expected reception level and the reception intensity of the receiver, and the difference between the actually expected reception signal level difference and the signal collision detection level difference. The received signal level difference is
Output deviation of LED4 and star coupler 1 from LED4
This is caused by a loss difference up to 0 (depending on the length and quantity of the optical fibers 5a, 5b, 5c, optical connector 3a, splice 9a, etc.) and a loss difference in the star coupler 10. Usually, in a system using the star coupler 10, the uplink.

Since the downlinks are installed with the same specifications, the signal level difference is % of the total loss except for the star coupler 10. From the light level diagram shown in Table 2, the signal collision detection level difference needs to increase with the received light power when the received light power is between -45 dBm and -34 dBm.

This occurs when the loss is greatest for the main signal in the uplink path and star coupler 10.

When the received light power is from -37 dBm to -34 dBm, the signal collision detection level difference needs to be 8 dB regardless of the received light power. During this period, the change in the received light level is determined by the star coupler 10.
This is caused only by the loss deviation of the path downstream from.

Next, the collision detection capability of the conventional transmitter/receiver with collision detection function will be described. First, the operation of setting the threshold voltage of the signal discriminator 14 will be explained. The level detection circuit 29
(1, -1) The output level of the filter 13 is monitored, and if the output level peak value exceeds the specified voltage input from the specified voltage input terminal 30, the output is held at "H", and if it does not exceed the specified voltage, the output is output. Hold “L”. The threshold voltage generation circuit 31 generates -Δ when the output of the level detection circuit 29 is “L”.
1. When it is "H", a threshold voltage of -Δ2 is generated and output to the signal discriminator 14. Here, -Δ2 times -Δ1. As a result, in Fig. 7, the PR (1
, -1) When the filter output 13a is inputted to the signal discriminator 14, the threshold voltage 15a becomes PR(
1, -1) When the filter output 13b is input to the signal discriminator 14, the threshold voltage 15b is supplied. Note that when the reception state ends, a pulse of a certain period of time is manually applied from the carrier-off circuit 32 to the level detection circuit 29, the output of the level detection circuit 29 is forced to "L", and the output of the threshold voltage generation circuit 31 becomes -Δ1. The device enters a reception standby state.

Now, suppose that the input of the specified voltage input terminal 30 is set to the received light power -3.
Assuming that the threshold voltage is set to switch from -Δ1 to -Δ2 at 5.5 dBm, and the threshold voltage -Δl is set to 137 dBm with the received light power, the signal collision detection level difference is 8 dB,
Assume that the threshold voltage -Δ2 is set so that the signal collision detection level difference is 8 dB when the received light power is -35.5 clBm. At this time, the relationship between the signal collision detection level difference, the threshold voltage, and the received light power is as shown in FIG. In Figure 8,
When the received light power is -37 dBm or more, the received light power -3
It can be seen that at points other than the 5.5 dBm point, the collision detection ability exceeds that required by the system.

Excessive collision detection ability becomes sensitive to even a slight waveform distortion of the O level, leading to the occurrence of erroneous collision detection on the side where the received light level is high.

[Problem that the invention seeks to solve]

Since the conventional transmitting/receiving device with a collision detection function is configured as described above, the LED driver 3. The preamplifier 12, the PR (1, -1) filter 13, etc. are required to have extremely low distortion characteristics, and there is a problem in that a large amount of test and adjustment time is required. In addition, the range of received light power in which erroneous detection of collision does not occur is limited by waveform distortion, and there is a problem that it cannot be widened.

This invention was made to solve the above-mentioned problems, and aims to provide a transmitter/receiver with a collision detection function that can shorten the test adjustment time and widen the range of received light power without causing erroneous collision detection. shall be.

[Means for solving problems]

The transmitting/receiving device according to the present invention includes a peak detector 15 that detects the output amplitude of the PR (L-1) filter 13, and a peak detector 15 that detects the output amplitude of the PR (L-1) filter 13 based on the output voltage of the peak detector 15 and a preset specified voltage. The signal discriminator 14 generates a constant threshold voltage when the output voltage of the peak detector 15 is smaller than the specified voltage, and generates a threshold voltage proportional to the output voltage of the peak detector 15 when the output voltage of the peak detector 15 is larger than the specified voltage.
The threshold voltage generation circuit 16 is provided with a threshold voltage generation circuit 16 for supplying the voltage to the voltage.

[Effect]

In this invention, since the output voltage of the peak detector 15 corresponds to the received light power, from the threshold voltage generation circuit 16,
When the received light power is less than the received light power corresponding to the specified voltage, a constant threshold voltage is output to the signal discriminator 14, and when the received light power is more than the received light power corresponding to the specified voltage, a threshold voltage proportional to the increase in the received light power is output. is output to the signal discriminator 14.

As a result, a stable collision detection operation can be obtained even in a region where the received light power is large.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a transmitting/receiving device according to an embodiment, and FIG.
The same reference numerals as in the conventional example in the figure indicate the same or equivalent parts.
The explanation will be omitted. In the figure, 15 is PR(1,-
1) a peak detector that detects the output amplitude of the filter 13;
16 is a threshold voltage generation circuit, 17 is a specified voltage input terminal, 18 is an operational amplifier, 19 is a transistor, 20.2
1 is a resistor, 22 is a reference voltage input terminal, and 23 is a constant current source.

In the operational amplifier 18, the potential of the specified voltage input terminal 17 is set so that the output becomes OV at the specified received light power, and the difference between the output of the peak detector 15 and the potential of the specified voltage input terminal 17 is determined by the transistor 19. Output to the base of. The potential of the reference voltage input terminal 22 of the transistor 19 is set so that the base input voltage switches at Ov, and when the base input voltage is positive, a collector current proportional to the base voltage flows through the resistor 20. , when the base input voltage is negative, the collector current becomes O. Therefore, when the received light power is less than the received light power corresponding to the potential of the specified voltage input terminal 17 of the operational amplifier 18, the output of the threshold voltage generation circuit 16 is the product of the current value of the constant current source 23 and the resistor 21, and - A certain threshold voltage is output to the signal discriminator 14. On the other hand, when the received light power is greater than the received light power corresponding to the potential of the specified voltage input terminal 17 of the operational amplifier 18, the current value of the constant current source 23, the received light power and the potential of the specified voltage input terminal 17 of the operational amplifier 18 Since the sum of current values proportional to the difference in received light power corresponding to flows through the resistor 21,
A threshold voltage proportional to the increase in received light power is output.

FIG. 2 is a peak detector detection characteristic diagram, FIG. 3 is a transistor static characteristic diagram, and FIG. 4 is a threshold voltage generation circuit input/output characteristic diagram, where 16a is the threshold voltage and 18a is the operational amplifier output. FIG. 5 is a diagram showing the signal collision detection level difference and threshold voltage versus received light power characteristics according to this embodiment.

Next, the operation will be explained in detail. Note that in FIG. 1, components having the same reference numerals as those in the conventional example operate in the same manner as in the conventional example, so a description thereof will be omitted. The peak detector 15 has PR(1,
-1) Detect the output amplitude of filter 13, and
Enter the date. It is assumed that the peak detector 15 has the peak detector detection characteristics shown in FIG. If the peak detector input amplitude is Vin (Vp-p) and the peak detector output voltage is Vout (V), then Vout - Vin + Vos
--(1). Here, Vos is a constant and the detection efficiency is 1. Specified voltage input terminal 1 of operational amplifier 18
7 is input with the output voltage of the peak detection wave 315 when the output amplitude VT of the PR (1, -1) filter 13 corresponding to the specified received light power P7 in equation (1) is input. Therefore, the output voltage Vop of the operational amplifier 18 is Vo
p= Vin −Vt −−(
2). The output voltage Vop of the operational amplifier 18 is input to the base of the transistor 19. It is assumed that the transistor 19 has transistor static characteristics shown in FIG. That is, the pace emitter voltage is a constant voltage Vll! When it is smaller, it is cut off, and when it is larger, it is conductive, and has a differential resistance r. The reference voltage input terminal 22 has a potential corresponding to the switching voltage VIIE of the transistor 19, that is, −
VIIE is given. At this time, if the resistance value of the resistor 20 is RE, then the collector current of the transistor 19 is 1
c is as follows.

The collector voltage Vc of the transistor 19 is as follows, where the resistance value of the resistor 21 is Rc, and the current value of the constant current source 23 is Io. From equation (4), the threshold voltage V tho becomes -RcIo when the received light power is smaller than the specified received light power of 2 units. Here, the resistance value R6 of the resistor 20 is calculated using the following formula.
From equation 4), when the received light power is larger than the specified light received power P, -.-(6) is obtained, and a threshold voltage that increases in proportion to the output amplitude of the PR (1, -1) filter 13 is obtained. (5) formula, (6)
From the equation, the threshold voltage generation circuit input/output characteristic diagram shown in FIG. 4 can be obtained. Here, suppose the specified received light power is 36.5 dB.
If we set the potential of the specified voltage input terminal 17 so that +++, and set the current value of the constant current source 23 so that the signal collision detection level difference is 8 dB at the received light power of 37.0 dBm, the signal collision detection level difference A characteristic diagram of the threshold voltage and the received light power is shown in FIG. Received power -36
, 5 dBm, the signal collision detection level difference increases in proportion to the received light power.

When the received light power becomes larger than -36.5 dBm, the threshold voltage 16a increases in proportion to the received light power as shown in equation (6), so the signal collision detection level difference remains constant at 8.5 dB regardless of the received light power. Become. In this way, the received light power is -36.
Even if the threshold voltage 16a is increased in proportion to the received light power at 5 dBm or more, the signal collision detection level difference required by the system is secured, and the influence increases in proportion to the received light power (PR (1, -1)). It is possible to cope with the waveform deterioration of the O level output from the filter 13, to obtain a wide range of received light power without causing erroneous collision detection, and to shorten the test adjustment time.

In the above explanation, the specified received light power is 36.5
dBm, but the same effect as above can be obtained regardless of the received light power as long as it is 37 dBm or more.

In addition, although we have described the case where the threshold voltage is set slightly below the O level of the PR (1, -1) filter output, it is also possible to set the threshold voltage slightly above the peak detector 15 shown in FIG. By using the threshold voltage generation circuit 16, the same effects as in the embodiment described here can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the peak detector 15 detects the output amplitude of the PR (1, -1) filter 13, and when the output voltage is equal to or higher than the specified voltage, the threshold voltage generation circuit 1
6 increases the threshold voltage of the signal discriminator 14 in proportion to the output voltage, thereby providing a transmitting/receiving device that has a wide range of light reception levels without causing erroneous collision detection while ensuring the signal collision detection level difference required by the system. This also has the effect of shortening the test adjustment time.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a peak detector detection characteristic diagram, Fig. 3 is a transistor static characteristic diagram, Fig. 4 is a threshold voltage generation circuit input/output characteristic diagram, and Fig. 5 The figure shows signal collision detection level difference and threshold voltage vs. received light power characteristics, Figure 6 is a configuration diagram of a conventional transmitting/receiving device, Figure 7 is an output waveform diagram of a partial response (1, -1) filter, and Figure 8 is a diagram of the output waveform of a partial response (1, -1) filter. FIG. 3 is a graph showing a conventional signal collision detection level difference and threshold voltage vs. received light power. In the figure, 1 is a signal input terminal, 2 is a dipulse encoding circuit,
3 is an LED driver, 4 is an LED, and 5a. 5b, 5c, 5d, 5e, 5f, 6c, 6d. 7C and 7d are optical fibers, 8a and 8b are optical connectors,
9a and 9b are splice points, 10 is a star turner, 1)
is an APD, 12 is a preamplifier, 13 is a partial response (1, -1) filter, 14 is a signal discriminator, 15 is a peak detector, 16 is a threshold voltage generation circuit, 17 is a specified voltage input terminal, 18 is an operational amplifier, 19 is a transistor,
20.21 is a resistor, 22 is a reference voltage input terminal, 23 is a constant current source, 24 is a collision detection circuit, 25 is a data reproduction output terminal, 26 is a collision detection pulse output terminal, 27 is a timing extraction circuit, 28 is a block synchronization It is a circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masu Oiwa (and 2 others) Figure 2
63 Country PR (1, -1) 75 Noshiyu and Kaji, Ina (■su) Akira 5 Figure Photoreceptor 77 [dya・prokJ Narrow 8th area photoreceptor power (dBmp=ak)

Claims (2)

[Claims] (1) The transmitter side is equipped with a dipulse encoding circuit that converts the packet transmission data sent to the communication path into a dipulse sequence, and the receiver side is equipped with a partial response (partial response) circuit that receives the transmission signal and converts it into AC according to a predetermined rule. 1,-1) A filter, a signal discriminator that is supplied with the output signal of this filter and identifies a signal with a threshold voltage slightly shifted from the zero level of the output signal, and after establishing synchronization for decoding the dipulse sequence, the above-mentioned In a transmitting/receiving device with a collision detection function, which is equipped with a collision detection circuit that detects a code transition rule violation based on a code string output from a signal discriminator and detects that a received packet is in a collision state, the partial response (1, -
1) A peak detector detects the output amplitude of the filter, and a constant threshold voltage is generated when the output voltage of the peak detector is smaller than the specified voltage based on the output voltage of this peak detector and a preset specified voltage. A transmitting/receiving device comprising: a threshold voltage generation circuit that generates a threshold voltage proportional to the output voltage of the peak detector and supplies it to a signal discriminator when the output voltage of the peak detector is higher than a specified voltage. (2) The threshold voltage generation circuit consists of an operational amplifier that outputs the difference between the output voltage of the peak detector and the specified voltage input from the specified voltage input terminal, and a circuit that shuts off when the output of this operational amplifier is negative and conducts when it is positive. a reference voltage input terminal that sets the switching level of this transistor, a resistor that sets the collector current value of the transistor, a resistor that generates a threshold voltage by flowing the collector current of the transistor, and a resistor that generates a threshold voltage by flowing the collector current of the transistor; 2. The transmitting/receiving device according to claim 1, further comprising a constant current source that supplies a constant current.