JPH0630083A - Transmission characteristic measuring instrument - Google Patents

Abstract

PURPOSE:To perform a test for a transmission line for a burst signal and the operation of an input/output part by forming the burst signal by attaching a fix bit signal on the forefront of generated data set as the target of an error test, and starting up the error test at a supplied start timing. CONSTITUTION:A transmitter 1 sends out a clock synchronized with a digital signal to be transmitted, i.e., a data clock on a route different from that for a measuring target 2. A receiver 3 reproduces the data from a reception signal synchronizing with the data clock received from such another route, and tests the error of reproduced data. A signal transmitted from the transmitter 1 is the burst signal in which the fix bit signal is attached on the forefront part of the data, and timing signals representing the start/completion of the burst signal, the start of significant transmission signal, and the start/completion of a fix code pattern, respectively are sent from the transmitter 1 to the receiver 3, and the receiver 3 measures the transmission characteristic of the measuring target 2 by using those timing signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used for testing a transmission line and its signal input section and signal output section.

In this specification, the signal input section or the signal output section of the transmission line means a circuit or an element for converting a signal inside the transmitter or the receiver and a signal on the transmission line. Examples of such a circuit or element include a modulator and a detector when the transmission path is an electrical transmission path, an electro-optical conversion element and an opto-electric conversion element when the transmission path is an optical transmission path. Further, peripheral circuits such as those bias circuits and preamplifiers may be included.

[0003]

2. Description of the Related Art As a device for measuring transmission characteristics of a transmission line and its signal input portion and signal output portion, conventionally, a signal input portion is connected to a transmitter and a signal output portion is connected to a receiver. A transmission characteristic measuring apparatus is used in which a test data signal is input from a transmitter and an error in the received signal is checked by a receiver.

In such a transmission characteristic measuring apparatus, as a test data signal transmitted from the transmitter, a code sequence signal obtained by sequentially generating codes by a predetermined generator polynomial, or a predetermined specified signal The signal of the code pattern (hereinafter referred to as “fixed code pattern signal”) is used. The transmitter inputs these data signals to the signal input section of the transmission line, adjusts the phase of the clock synchronized with the data signal, and sends the clock to the receiver.
The phase of the clock is adjusted because there is a phase difference with the system under measurement, and the phase of the clock may be adjusted not by the transmitter but by the receiver. The output data signal of the transmitter is sent from the signal input section to the transmission path, and is output from the signal output section to the receiver.

The receiver reproduces the received signal from the signal output section by the clock from the transmitter, further performs a sequence check if it is a code sequence signal, and if it is a fixed code pattern signal, stores it in its own memory. Check the error by comparing it with the fixed pattern you are doing. The receiver is also provided with circuitry to match the "0", "1" thresholds in the input data with the thresholds in the device.

Whether a code sequence signal or a fixed code pattern signal is used, an error rate and an error free time are obtained as a measurement result and used as a transmission characteristic.

A pseudo-random code sequence (PRBS) is well known as a typical code sequence used for measuring transmission characteristics. In the signal of the code sequence, if the synchronization can be established in the first few bits, the signals are sequentially determined thereafter.
On the receiving side, after synchronization, the error from the code sequence is counted and the transmission system is inspected. In the case of a fixed code pattern signal, it is transmitted continuously or by inserting it at a predetermined position, and the receiving side detects an error by comparing it with a previously stored pattern and counts it.

[0008]

In such a measuring apparatus, in the transmitter, either a code sequence signal, a fixed code pattern signal, or a signal in which a fixed signal is inserted by designating a particular place in the code sequence signal is used. To use. Whichever signal is used, the signal transmitted by the transmitter is a continuous signal. Here, "continuous" means that even if only one of the output values "0" or "1" is continuous, a signal is present almost on average. That is, the transmission characteristics have been measured with the transmission line and its signal input section and signal output section already synchronized.

However, such a device is not suitable for measuring the transmission characteristics of a signal such as a packet or a cell which is generated asynchronously and in a burst.

The burst signal transmission device cannot predetermine when the burst signal is generated or when it is received. For this reason, at the time of transition from a state where there is no signal to a state where there is a signal, the state of the signal input unit or signal output unit of the transmission line, or in some cases the transmission line itself, changes. Further, in the absence of a signal, the signal conversion element of the signal input section or the signal output section and its peripheral circuits may be in a standby state. Due to such circumstances, accurate reception is not generally guaranteed for the first few bits of the burst signal. Therefore, in a normal burst signal transmission device, a bit for pulling in synchronization at the receiving side is added to the head of the burst signal, and some of these bits are allowed to be lost, and synchronization is pulled in at each burst occurrence. .

If this is also applied to the conventional transmission characteristic measuring apparatus, the signal after the synchronization pull-in can be measured. However, it is not possible to measure the bit for synchronization pull-in.

It is an object of the present invention to solve the above problems and to provide a transmission characteristic measuring apparatus capable of measuring the transmission characteristic of a transmission line for a burst signal and its signal input / output section.

[0013]

According to the transmission characteristic measuring apparatus of the present invention, a transmitter generates data to be error-checked by an error-checking means of a receiver, and a head part of the generated data. The receiver includes means for adding a fixed bit signal to form a burst signal, and means for notifying the receiver of the start timing of data to be error-checked included in the burst signal. It is characterized by including means for activating the error checking means at the start timing notified by.

The means for generating data in the transmitter includes a code sequence generating section for sequentially generating codes according to a predetermined generator polynomial, a fixed code pattern generating section for generating codes of a predetermined fixed pattern, The error checking means includes a means for selecting and operating either the code sequence generating section or the fixed code pattern generating section and a code selection notifying means for notifying the receiver of the timing of this selection. A code sequence signal error check circuit for checking an error in the received and reproduced data by generating a code by the same logic as the code sequence generation unit based on the data, and received and reproduced by comparing with a code stored in advance. And a fixed code pattern signal error check circuit for checking an error in the selected data, and means for activating the code selection notification. It is possible to include a means for controlling the operation timing of the code sequence signal error check circuit and the fixed code pattern signal error check circuit by notification from the stage.

[0015]

The error rate is not checked for all signals using continuous signals, but data unrelated to error measurement is added so that the receiver side does not check for data errors at that timing. Data that is not related to error measurement is not the bit for synchronization pull-in that is used in ordinary burst signal transmission equipment, but is simply the bit provided at the beginning of the burst signal, and usually the number of bits for synchronization pull-in. Grant much less bits, for example a few bits. By adding such bits, it is possible to check the transmission error of bits used for synchronization pull-in in normal burst signal transmission, except for the first few bits.

Specifically, the timing of the signal to be evaluated in the burst signal is notified from the transmitting side to the receiving side. An error rate test is performed using a code sequence signal, and there is a fixed code pattern signal and a signal indicating the timing at which the code sequence signal exists so that normal operation can be confirmed even if a specific code string is included. Both the signal indicating the timing is used. On the receiving side, the checking method is switched according to these timing signals, and the code sequence check and the fixed pattern check are performed.

The fixed code pattern signal is used because, for example, when the data "0" continues, the transmission system to be measured does not consider it as the burst end, or the gain adjustment of the level adjustment circuit is abnormal. This is to check if there is nothing to consider. Such a check is indispensable in a burst signal transmission device.

Although switching between the code sequence signal and the fixed code pattern signal has been performed conventionally, it is performed every measurement, and two kinds of signals are mixed in a continuous signal. There wasn't. On the other hand, in the present invention, by transmitting the timing signal from the transmitter to the receiver, two types of signals can be mixed and the transmission characteristics for burst signals can be measured in detail.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of the present invention, and is a block diagram showing the overall configuration of a transmission measuring and measuring apparatus.

In the apparatus of this embodiment, a transmission line and a signal input section and a signal output section of the transmission line are set as measurement targets 2, and a transmitter 1 that outputs a digital signal to the signal input section and an output from the signal output section. And a receiver 3 for receiving the signal. The transmitter 1 uses a clock signal synchronized with a digital signal to be transmitted, that is, a data clock as a measurement target 2
It is sent via a route different from. The receiver 3 reproduces the data from the received signal in synchronization with the data clock received from this other path, and checks the reproduced data for errors.

The feature of this embodiment is that the signal transmitted by the transmitter 1 is a burst signal in which a fixed bit signal is added to the beginning of data, and the burst signal is transmitted from the transmitter 1 to the receiver 3. Timing signals indicating the start and end of a signal, the start of a significant transmission signal, and the start and end of a fixed code pattern are sent, and the receiver 3 uses these timing signals to measure the transmission characteristics of the measurement target 2. Is. This will be described in more detail.

FIG. 2 is a block diagram showing an example of the transmitter 1.

The transmitter 1 is provided with a clock generator 11 for generating a clock for signal transmission and outputting the generated clock as a data clock, and a timing controller 12 for controlling operation timing. The data clock output by the clock generator 11 is
It is sent to the receiver 3 via the gate circuit 22 and a phase adjustment circuit (not shown).

The transmitter 1 further includes a code sequence generation unit 14, a fixed code pattern generation unit 15 and gate circuits 18, 20, 21 as means for generating data to be error-checked in the receiver 3 and generated. The gate circuits 17 and 19 and the fixed bit generation unit 1 serve as means for adding a fixed bit signal to the beginning of the data to form a burst signal.
3 and the burst synthesizing unit 16, the timing control unit 12 is provided with means for notifying the receiver 3 of the start timing of the data included in the burst signal which is the object of error checking, that is, the significant transmission signal.

When the burst control signal is output from the timing control section 12, the fixed bit generation section 13 continues until the significant transmission signal start signal is output.
The fixed bit is output in synchronization with the clock from 1.

When the timing control unit 12 outputs the significant transmission signal start signal, the code sequence generation unit 14 operates in synchronization with the clock from the clock generation unit 11 unless a fixed code pattern start signal is output. Random code sequence (PRBS) signals are sequentially output. When the fixed code pattern start signal is output, the code sequence generation unit 1
4 temporarily stops the output and restarts the generation of the code sequence signal after the signal of the fixed code pattern end is output. The generation of the code sequence signal is continued until the end of the burst.

When the fixed code pattern start signal is output from the timing control unit 12, the fixed code pattern generation unit 15 generates the fixed code pattern signal until the next fixed code pattern end signal is output.

The burst synthesizing unit 16 synthesizes the signals selectively output from the fixed bit generating unit 13, the code sequence generating unit 14 and the fixed code pattern generating unit 15 into a burst signal, and uses it as a clock from the clock generating unit 11. Output to the measurement target 2 in synchronization.

Fixed bit generator 13 and code sequence generator 1
4 and the operation of the fixed code pattern generation unit 15 are selected by a combination of the timing signals of the burst start and end, the significant transmission signal start, and the fixed code pattern start and end output from the timing control unit 12. In FIG. 2, as an example of a circuit for performing this selection, an example using gate circuits 17 to 21 by AND circuits is shown. Each timing signal is also sent to the receiver 3 via a phase adjustment circuit (not shown).

FIG. 3 is a block diagram showing an example of the receiver 3.

The receiver 3 includes a data reproducing section 31 for reproducing data from the received signal in synchronization with a clock signal received from a path different from the object to be measured 2, and an error check for inspecting an error in the reproduced data. A code sequence signal error check circuit 33 and a fixed code pattern signal error check circuit 35 are provided as means.

The code sequence signal error check circuit 33 generates a code based on the received and reproduced data by the same logic as the code sequence generation unit 14 on the transmitting side, and inspects the error of the received and reproduced data. . The fixed code pattern signal error check circuit 35 checks the error of the received and reproduced data by comparing with the code stored in advance. These inspection results are output as measurement results such as error rate and error free time.

The receiver 3 further includes gate circuits 36, 37, 38 and a shift circuit as means for controlling the operation timings of the code sequence signal error check circuit 33 and the fixed code pattern signal error check circuit 35 according to the notification from the transmitter 1. The registers 32 and 34 are provided.

The gate circuits 36 and 37 receive a significant transmission signal start signal from the transmission side and a fixed code pattern start signal has not yet arrived, or a fixed code pattern end signal has already arrived. , Data clock is supplied to the shift register 32. Gate circuit 38
Supplies the data clock to the shift register 34 from the arrival of the fixed code pattern start signal to the arrival of the end signal thereof. The shift registers 32 and 34 output the reproduced data by 1 each time the data clock is input.
Capture bit by bit and output sequentially. Therefore, the part of the code sequence signal is taken out by the shift register 32 and sent to the code sequence signal error check circuit 33, and the part of the fixed code pattern signal is taken out by the shift register 34 and supplied to the fixed code pattern signal error check circuit 35. To be done.

FIG. 4 shows a timing chart of each signal.

The burst signal used here is shown in FIG.
As shown in, the fixed additional bits and the test transmission signal are included. The fixed additional bits do not include a signal to be transmitted and are not subject to measurement of transmission characteristics such as error rate counting. Since the fixed additional bit is mainly used for setting up a receiving side circuit or device, it is usually added to the head of the burst signal. The number of bits and bit pattern are determined by the conditions of the transmission path to be measured (and the transmission device connected to it). Further, if this additional bit is measured by using the clock transmitted through another path, the rising characteristic can be measured.

The start and end of the burst, the start of the significant transmission signal, and the start and end of the fixed code pattern are represented by the rising and falling edges of the signals shown in FIGS. 4B, 4C and 4D, respectively. It However, the end of the significant transmission signal coincides with the end of the burst.

The signal of the start of the Barts is not always necessary because the measurement is performed only on the portion of the significant transmission signal, but for example, the receiver 3 makes a logical decision at the beginning of the burst reception to determine the transmission line up to that point. It can also be used as a reset signal in the case of resetting the receiving circuit state and starting the operation.

The data clock is sent from the transmitter 1 to the receiver 3 only when the significant transmission signal is transmitted in the burst as shown in FIG. 4 (e). Transmission and reception of the data clock is basically sufficient for this time range,
The entire burst period or a continuous clock may be sent.

In the above embodiment, in order to simplify the explanation, signals from the transmitter 1 to the receiver 3 are provided which correspond to the burst signal, the significant transmission signal and the fixed code pattern signal and have a constant potential state therebetween. An example was sent to. However, practically, each timing is set from the transmitter 1 to the receiver 3
It is enough to notify. Such an example is shown in FIG.

FIG. 5 is a diagram showing the relationship between the burst signal, the timing signal and the data clock.

The burst signal shown in FIG. 5A is shown in FIG.
It is equivalent to that shown in (a). However, in the case of the example shown in FIG. 5, a burst start, a start of a significant transmission signal (code sequence signal), a start point and an end point of the inserted fixed code pattern, and a burst end position are formed by a series of timing pulses. Represent In this example, the fixed code pattern signal is arranged between the code sequence signals, but the significant transmission signal may start with the fixed code pattern, and in that case, the signal indicating that signal comes first. . These timing pulses may be transmitted using physically different signal lines, but the common signal line can be used and the meaning thereof can be distinguished by changing the pulse intensity or its width.

When such a timing pulse is used, it is necessary to modify the configuration shown in FIGS.
This correction can be easily realized by using a circuit that is enabled by one timing pulse and disabled by the next pulse.

Some burst signal transmission devices have a certain burst cycle, and communication is performed by repeatedly sending bursts at each burst cycle. An example of the burst signal in such a case is shown in FIG.

In such a burst signal transmission device, setup is required at the start of communication, such as activation of peripheral devices, adjustment of the transmission signal level on the transmission side, and level adjustment by signal level detection on the reception side. Therefore, the transmission system may not be established for the first one or a few bursts, and it is allowed that the initial burst does not operate normally as a whole.

In order to measure the transmission characteristics of the transmission line and its signal input / output section in such an apparatus, it is necessary to determine whether or not the transmission characteristics of a specific burst, in this case, the first burst or bursts. Must be specified. This can be done by setting the clock on the transmitter side so that the transmission characteristic is measured as a burst signal when the timing signal arrives, and not measured when it does not arrive.

[0047]

As described above, the transmission characteristic measuring apparatus according to the present invention does not check the error rate for all signals using continuous signals, but adds data unrelated to the error measurement. The timing is sent from the transmitter to the receiver so that the receiver does not check for data errors. This enables an operation test of the transmission line for the burst signal and its signal input / output unit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a transmitter.

FIG. 3 is a block configuration diagram showing an example of a receiver.

FIG. 4 is a diagram showing timing of signals.

FIG. 5 is a diagram showing timing when a timing pulse is used.

FIG. 6 is a diagram showing an example in which a burst occurs in each cycle.

[Explanation of symbols]

 1 Transmitter 2 Measurement Target 3 Receiver 11 Clock Generation Section 12 Timing Control Section 13 Fixed Bit Generation Section 14 Code Sequence Generation Section 15 Fixed Code Pattern Generation Section 16 Burst Synthesis Section 17-22, 36-38 Gate Circuit 31 Data Recovery Section 32, 34 shift register 33 code sequence signal error check circuit 35 fixed code pattern signal error check circuit

Claims (2)

[Claims] 1. A transmitter for measuring a transmission line and a signal input unit and a signal output unit of the transmission line, which outputs a digital signal to the signal input unit, and receives a signal output from the signal output unit. A receiver, the transmitter includes means for transmitting a clock signal synchronized with a digital signal to be transmitted through a path different from the measurement target, and the receiver includes a clock signal received through the different path. In a transmission characteristic measuring device including a data reproducing unit that reproduces data from a received signal in synchronization with the error detection unit and an error checking unit that checks an error in the reproduced data, the transmitter includes an error checking unit in the error checking unit. Means for generating target data, means for adding a fixed bit signal to the beginning of the generated data to form a burst signal, and errors included in the burst signal Means for notifying the receiver of the start timing of the data to be inspected, wherein the receiver includes means for activating the error checking means at the start timing notified by the notifying means. And a transmission characteristic measuring device. 2. The means for generating the data comprises: a code sequence generation unit that sequentially generates a code according to a predetermined generator polynomial; a fixed code pattern generation unit that generates a code of a predetermined fixed pattern; The error checking means includes a means for selecting and operating either the code sequence generating section or the fixed code pattern generating section, and code selection notifying means for notifying the receiver of the timing of this selection. A code sequence signal error check circuit for checking an error of the received and reproduced data by generating a code by the same logic as the code sequence generation unit based on the reproduced data, and comparing it with a code stored in advance. A fixed code pattern signal error check circuit for checking an error in the data received and reproduced by the Means, transmission characteristic measuring apparatus of claim 1 further comprising means for controlling the operation timing of the code sequence signal error checking circuit and said fixed code pattern signal error check circuit by a notification from the code selection notifying means.