JP5345567B2 - Error rate measuring apparatus and method - Google Patents

Description

  The present invention inputs a test signal of a predetermined pattern to a device under test, receives an optical signal from the device under test accompanying the input of the test signal, and performs a plurality of measurements including waveform error measurement (waveform measurement / display, The present invention relates to an error rate measuring apparatus and method for simultaneously performing jitter measurement and the like.

  In recent years, various types of digital wired communication devices are required to have a larger capacity transmission capability with the increase in the number of users and the spread of multimedia communication. As an index for evaluating the quality of digital signals in these digital wired communication apparatuses, a bit error rate (Bit Error Rate) defined as a comparison between the number of received code errors and the total number of received data. )It has been known.

  In addition, a test signal including fixed data is sent to the device under test (Device Under Test), such as a photoelectric conversion component to be tested, and the signal under measurement input via the device under test and a reference signal as a reference For example, an error rate measuring apparatus as disclosed in the following Patent Document 1 is known as a measuring device that detects the error rate of a signal under measurement by comparing each of the above with a bit unit.

  FIG. 2 is a schematic configuration diagram of an error rate measuring apparatus disclosed in Patent Document 1 below. As shown in the figure, the bit error measuring apparatus 100 includes a data storage unit 101 configured by a memory such as a RAM, a comparison data storage unit 102, a position information storage unit 103, and a signal transmission unit 104 configured by an integrated circuit or the like. , A signal reception unit 105, a synchronization detection unit 106, a comparison unit 107, a display control unit 108, a display device 109 such as a CRT or a liquid crystal display, and an operation unit 110 such as a keyboard. In bit error measuring apparatus 100 that measures error bits by comparing data with known data to be received from measurement object 200, comparison data storage unit 101 having a plurality of blocks, received input data, and known data And a ratio of bit strings including one or more detection bits detected under a predetermined detection condition The comparison unit 102 that sequentially stores data in a plurality of blocks according to detection, and each bit string obtained from the comparison data stored in each of the plurality of blocks is based on a position according to a predetermined arrangement condition And a display control unit 104 that displays them side by side on the display device 103.

JP 2007-274474 A

  Conventionally, when the error rate of a device under test is measured using the error rate measuring apparatus described above, if an abnormality is found in the measurement result, a waveform display measuring instrument such as a sampling oscilloscope is separately used to measure from the device under test. However, it has been desired to measure the error rate of these devices under test and to measure and display the waveform of the signal with a single signal input.

  By the way, filters that remove signal components other than the desired band are used in various fields, and particularly in the optical communication field, in the receiver such as the error rate measuring apparatus and the waveform display measuring instrument described above, the noise component of the signal. The standard uses a 4th order Bessel-Thomson Low-Pass-Filter (hereinafter abbreviated as BT-LPF) having a cut-off frequency of 75% of the signal bit rate (signal transmission speed) in order to eliminate ringing and prevent ringing. It is prescribed. For example, ITU-TG In 957, the fourth order Bessel LPF is defined as the characteristic of the reference receiver, and is defined up to the error range of the frequency characteristic. For this reason, it is necessary to use BT-LPF in the receivers of various measuring instruments including the error rate measuring apparatus described above.

  However, since each measuring device supports various standard bit rates so that measurement can be performed at various frequencies, BT-LPFs are required for the types of standard bit rates. In addition, the standard requires the BT-LPF characteristics as the characteristics of the entire receiver, so it is necessary to design the entire receiving system, not the filter alone, for each receiving system (each measuring instrument). There is a need to design.

  In addition, in waveform display measuring instruments (sampling oscilloscopes) that display the waveform of the measured signal in time series, there are systems that use a built-in filter as a reference receiver, but other measuring instruments, especially the error rate measurement described above, are available. There has been no device that has positively changed the reception system characteristics to the BT-LPF system.

  Therefore, the present invention has been made in view of the above problems, and can be simplified for design and adjustment without the need for filter replacement and the like, and can be shared by a receiving system in a plurality of measurements including error rate measurement. An object of the present invention is to provide an error rate measuring apparatus and method.

In order to achieve the above object, an error rate measuring apparatus according to claim 1 of the present invention receives an optical signal as a signal under measurement from the device under test W accompanying the input of a test signal with a predetermined pulse pattern. One input terminal 1a ;
A photoelectric conversion unit 2 that converts an optical signal input from the one input terminal into an electrical signal;
A filter 5a composed of a low-pass filter having a Bessel-Thomson characteristic having a cutoff frequency corresponding to each standard bit rate specified by the standard, and a semiconductor resistor or capacitor having a high-pass filter characteristic disposed before and after the filter A frequency characteristic adjusting unit 5 provided with a plurality of pairs in a pair with the equalizer 5b;
A plurality of measuring units 7 for simultaneously performing a plurality of measurements including an error rate based on a signal converted into an electrical signal by the photoelectric conversion unit and passed through the filter ;
Provided front and rear stages before Symbol frequency characteristic adjuster, the frequency characteristic adjusting section select the frequency characteristic adjusting section corresponding to a predetermined standard bit rate unison with the contacts to switch the path of the high frequency signal switching control The high-frequency switching units 3a and 3b,
A branching unit 6 for equally branching a signal whose frequency characteristic is adjusted by the frequency characteristic adjusting unit and being input via the high-frequency switching unit and outputting to each of the plurality of measuring units ;
The equalizer adjusts a frequency characteristic so as to correct characteristic deterioration that occurs in the photoelectric conversion unit, the high-frequency switching unit, and the branching unit .

According to the error rate measuring method of the second aspect, an optical signal is input from one input terminal 1a as a signal under measurement from the device under test W accompanying the input of a test signal with a predetermined pulse pattern, An error rate measurement method in which a plurality of measurements including an error rate are simultaneously performed by a plurality of measurement units 7 based on an input signal,
Converting an optical signal input from the one input end into an electric signal by the photoelectric conversion unit 2 ;
A filter 5a composed of a low-pass filter having a Bessel-Thomson characteristic having a cutoff frequency corresponding to each standard bit rate specified by the standard , and a semiconductor resistor or capacitor having a high-pass filter characteristic disposed before and after the filter In order to select a frequency characteristic adjustment unit corresponding to a predetermined standard bit rate from the frequency characteristic adjustment unit 5 provided in a pair with a pair of equalizers 5b and to switch the path of the high frequency signal, A step of controlling opening and closing of the contacts of the high-frequency switching units 3a and 3b provided in the subsequent stage,
A step of equivalently branching the signal having the adjusted frequency characteristic by the branching unit 6 and outputting to each of the plurality of measurement units ;
And adjusting the frequency characteristics so as to correct the characteristic deterioration that occurs in the photoelectric conversion unit, the high-frequency switching unit, and the branch unit by the equalizer .

  According to the present invention, it is possible to select a filter corresponding to a standard bit rate in software, and it is possible to save the user from changing the filter. In addition, high-frequency switches and cable losses, characteristics of the photoelectric exchange elements used, such as photodiodes (PD), and characteristic deterioration due to branch circuits can be corrected to make BT-LPF when viewed as a whole system. Can be shared by the receiving system in a plurality of measurements.

It is a block block diagram of the error rate measuring apparatus which concerns on this invention. It is a schematic block diagram which shows an example of the conventional error rate measuring device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an error rate measuring apparatus according to the present invention.

  As shown in FIG. 1, the error rate measuring apparatus 1 according to the present invention receives an optical signal as a signal under measurement from the device under test W accompanying the input of the test signal from the test signal generator 11 to the device under test W. The input terminal 1a is composed of a photoelectric conversion unit 2, a high frequency switching unit 3, a control unit 4, a frequency characteristic adjustment unit 5, a branching unit 6, and a measurement unit 7 in the subsequent stage. .

  The photoelectric conversion unit 2 includes, for example, a photodiode (PD), and converts an optical signal input from one input terminal 1a into an electric signal.

  The high frequency switching unit 3 is configured by a high frequency relay or a high frequency switch corresponding to a high frequency of 26 GHz, for example. The high-frequency switching unit 3 includes an input-side high-frequency switching unit 3a provided before the frequency characteristic adjusting unit 5 and an output-side high-frequency switching unit 3b provided after the frequency characteristic adjusting unit 5, and each contact point. Is controlled in conjunction with the control unit 4.

The control unit 4 selects one frequency characteristic adjustment unit 5 (filter 5a to be described later) corresponding to a predetermined standard bit rate and switches the high-frequency signal path to switch the input-side and output-side high-frequency switching units 3a and 3b. Open / close control is performed in software by linking the contacts.

  In the frequency characteristic adjusting unit 5, a plurality of sets of the filter 5a and the equalizer 5b are connected in parallel between the input-side high-frequency switching unit 3a and the output-side high-frequency switching unit 3b. The plurality of pairs of filters 5a and equalizers 5b correspond to the respective standard bit rates defined by the standard.

  The filter 5a is composed of a low-pass filter, attenuates and blocks a frequency signal higher than a specific threshold, and allows only a low frequency to pass as a signal.

The equalizer 5b is composed of semiconductor resistors and capacitors having high-pass filter characteristics arranged before and after the filter 5a. The equalizer 5b adjusts the resistance value of the semiconductor resistor by changing the resistance value so as to satisfy the standard by utilizing the characteristics of the filter 5a. 3 (high-frequency relay or high-frequency switch), cable loss, characteristics of the photoelectric conversion unit 2 (PD) used, and characteristic deterioration due to the branching unit 6 are corrected.

  The branching unit 6 divides the signal whose characteristic has been extended to a high frequency by the frequency characteristic adjusting unit 5 equivalently by a resistor and outputs it to the measuring unit 7. In the example of FIG. 1, the signal from the frequency characteristic adjustment unit 5 is equivalently branched into two and output to the measurement unit 7.

  The measuring unit 7 performs various measurements based on the signals branched equally by the branching unit 6. In the example of FIG. 1, the measurement unit 7 includes an error measurement unit 7a and a waveform display unit 7b.

  When the signal branched by the branching unit 6 is input, the error measuring unit 7a compares the signal with the test signal input to the device under test W and measures the bit error of the signal.

  The waveform display unit 7b is obtained by sampling a signal from the branch unit 6 into the internal memory as waveform data and discretely sampling an event in which the voltage or current value changes with time, such as a sampling oscilloscope. A waveform image based on the waveform data is reproduced and displayed on the display screen in a display form desired by the user.

  As described above, the error rate measuring apparatus 1 of the present example is configured to switch and control the contacts of the high-frequency switching unit 3 (3a, 3b) including a high-frequency switch and a high-frequency relay. As a result, it is possible to select the filter 5a corresponding to the standard bit rate in a software manner, and it is possible to save the user from changing the filter.

  In addition, when looking at the entire system, the frequency characteristics of the high-frequency switching unit 3 and cable loss, the characteristics of the photodiode (photoelectric conversion unit) used, and the characteristic deterioration due to the branching unit 6 are BT-LPF. It can be corrected by the equalizer 5b of the adjustment unit 5.

  Further, the output of the branch unit 6 at the final stage is internally connected to the error measurement unit 7a and the waveform display unit 7b constituting the measurement unit 7, and the receiving system of both the error measurement unit 7a and the waveform display unit 7b. Are connected to the same signal. As a result, the characteristics formed by the high frequency switching unit 3 (3a, 3b) including a high frequency switch or a high frequency relay and the frequency characteristic adjusting unit 5 including the filter 5a and the equalizer 5b can be shared in a plurality of measurements including error measurement. It becomes a configuration, and it becomes possible to measure errors in a receiving system compliant with a standard that has not existed before.

  Normally, it is necessary to design as many as the number of receiving systems, but in the error rate measuring apparatus 1 of this example, the configuration between the photoelectric conversion unit 2 and the measurement unit 7 (high frequency switching unit 3, frequency characteristic adjustment unit) 4. Since the control unit 5 and the branch unit 6) are shared by all systems, design and adjustment can be simplified by reducing costs, and error measurement and waveform display can be performed with the same waveform. It is possible to cope with a plurality of measurements such as visualization of the waveform under measurement.

  By the way, in embodiment mentioned above, although the measurement part 7 is comprised by the error measurement part 7a and the waveform display part 7b, if the various measurement of the optical signal input from one input terminal 1a is performed, It is not limited to the configuration of FIG. For example, the error measurement unit 7a and the waveform display unit 7b may further include a jitter measurement unit that measures a temporal shift or fluctuation of a signal. Further, the measurement unit 7 can be configured by the error measurement unit 7a and the jitter measurement unit.

DESCRIPTION OF SYMBOLS 1 Error rate measuring device 2 Photoelectric conversion part 3 (3a, 3b) High frequency switching part 4 Frequency characteristic adjustment part 4a Equalizer 4b Filter 5 Control part 6 Branch part 7 Measurement part 7a Error measurement part 7b Waveform display part 11 Test signal generation part W Device under test

Claims (2)

One input terminal (1a) to which an optical signal is input as a signal under measurement from the device under test (W) accompanying the input of a test signal with a predetermined pulse pattern ;
A photoelectric conversion unit (2) for converting an optical signal input from the one input terminal into an electric signal;
A filter (5a) comprising a low-pass filter having a Bessel-Thomson characteristic having a cutoff frequency corresponding to each standard bit rate specified by the standard, and a high-pass filter characteristic semiconductor resistor and capacitor disposed before and after the filter A frequency characteristic adjusting unit (5) provided in pairs with an equalizer (5b) comprising:
A plurality of measurement units (7) for simultaneously performing a plurality of measurements including an error rate based on a signal converted into an electrical signal by the photoelectric conversion unit and passed through the filter ;
Provided front and rear stages before Symbol frequency characteristic adjuster, the frequency characteristic adjusting section select the frequency characteristic adjusting section corresponding to a predetermined standard bit rate unison with the contacts to switch the path of the high frequency signal switching control The high-frequency switching unit (3a, 3b)
A branching unit (6) for adjusting a frequency characteristic in the frequency characteristic adjusting unit and branching a signal input through the high-frequency switching unit in an equivalent manner to each of the plurality of measuring units ;
The error rate measuring apparatus , wherein the equalizer adjusts a frequency characteristic so as to correct characteristic deterioration that occurs in the photoelectric conversion unit, the high-frequency switching unit, and the branching unit . An optical signal is input from one input terminal (1a) as a signal under measurement from the device under test (W) accompanying the input of a test signal with a predetermined pulse pattern, and the error rate is based on the signal input to the input terminal. An error rate measurement method for simultaneously performing a plurality of measurements including a plurality of measurement units (7),
A step of converting an optical signal input from the one input end into an electric signal by a photoelectric conversion unit (2) ;
A filter (5a) comprising a low-pass filter having a Bessel-Thomson characteristic having a cutoff frequency corresponding to each standard bit rate specified by the standard , and a high-pass filter characteristic semiconductor resistor and capacitor disposed before and after the filter In order to select a frequency characteristic adjustment unit corresponding to a predetermined standard bit rate from a frequency characteristic adjustment unit (5) provided in pairs with an equalizer (5b) consisting of A step of controlling the opening and closing of the contact points of the high-frequency switching units (3a, 3b) provided at the front stage and the rear stage of the characteristic adjustment unit;
A step of equally branching the signal whose frequency characteristic is adjusted by the branching unit (6) and outputting the signal to the plurality of measuring units ,
Adjusting the frequency characteristic so as to correct the characteristic deterioration caused in the photoelectric conversion unit, the high-frequency switching unit, and the branch unit by the equalizer .

Images