KR100350234B1 - Method for monitoring of bit error rate using the power of clock component - Google Patents

Abstract

The present invention relates to a method of measuring an error rate of a signal using the power of a clock component. More particularly, to a technique capable of measuring error rate information of an optical signal required for operation / maintenance of an optical communication system and an all-optical transmission network.

The conventional error rate measurement method does not provide all the information necessary for system operation / maintenance. The distortion of the signal itself can not be known even when the optical signal-to-noise ratio (OSNR) is measured. Therefore, there is a need for a new measurement method that can easily measure the error rate to know the quality of the perfect signal in digital communication.

Accordingly, the present invention provides: 1) extracting a clock component of data from a transmitted optical signal and measuring a magnitude thereof to convert an eye open penalty; 2) Optical signal-to-noise ratio is measured by optical signal-to-noise ratio measurement method proposed by several methods; 3) A method of measuring the error rate of a signal using the power of a clock component that can measure an error rate of an optical signal by calculating an error rate with optical signal-to-noise ratio, eye openness penalty, and signal power.

Accordingly, the present invention not only facilitates the operation / maintenance of the optical communication system and the optical transmission network using the optical amplifier, but also contributes to the improvement of the reliability of such a system. Further, the present invention can be applied not only to an optical communication system but also to a general digital communication system.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of measuring an error rate of a signal using power of a clock component,

The present invention relates to a method of measuring an error rate of a signal using the power of a clock component. More particularly, to a technique capable of measuring error rate information of an optical signal required for operation / maintenance of an optical communication system and an all-optical transmission network.

The transmission distance of the optical communication system is remarkably increased as the optical amplifier capable of directly amplifying the light is commercialized, and the optical transmission system in which the transmission distance of no relay is several hundred km is commercialized.

In addition, researches on an all-optical transmission network that performs circuit distribution and branch combining in an optical signal state without converting an optical signal into an electric signal are actively under way. Such an all-optical transmission network is expected to be used as a time transmission network in the upcoming information age.

In order to utilize such a system, it is necessary to operate / maintain the system based on accurate information about the performance of optical signal transmitting information, that is, signal strength, signal-to-noise ratio, error rate when receiving signals, Should be able to.

In conventional optical communication networks that do not use optical amplifiers, a repeater relaying optical signals or a terminal receiving optical signals converts an optical signal into an electrical signal, thereby accurately measuring information about the performance of the optical signal required to maintain the operation of the system I could.

However, a system using an optical amplifier does not convert an optical signal into an electrical signal in a repeater because an optical amplifier repeater is used instead of a conventional electrical repeater. Also, at the nodes of the all - optical transmission network, the optical signals are not converted into electrical signals, but branching or circuit distribution is performed in the optical signal state.

Therefore, a method for measuring information about the performance of the optical signal required to maintain the operation of the system or network should be developed.

Also, existing methods do not provide all the information needed to operate / maintain the system. For example, in the optical signal intensity measurement method which is initially proposed, if the optical signal does not include data, it is determined that the intensity of the optical signal is normal but it is impossible to actually communicate.

In order to compensate for this, in the case of the proposed optical signal-to-noise ratio (OSNR) measurement method, the distortion of the signal itself can not be known. Therefore, there is a need for a new measurement method that can easily measure the error rate to know the quality of the perfect signal in digital communication.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an optical transmission system using an optical amplifier or a signal using a power of a clock component capable of measuring an error rate of an optical signal, And a method for measuring an error rate.

Technical Solution In order to accomplish the above object of the present invention,

1) extracting a clock component of the data from the transmitted optical signal and measuring the size thereof to convert the eye opening penalty; 2) Optical signal-to-noise ratio is measured by optical signal-to-noise ratio measurement method proposed by several methods; 3) A method of measuring the error rate of a signal using the power of a clock component that can measure an error rate of an optical signal by calculating an error rate with optical signal-to-noise ratio, eye openness penalty, and signal power.

1 is a block diagram showing an apparatus for measuring a signal error rate using the power of a clock component according to the present invention.

2A to 2F are diagrams showing waveforms of respective signals measured from the optical signal error rate measuring apparatus when the input optical signal is an NRZ signal

3 is a graph showing a result of a simulation in which an eye opening penalty is converted to a power of a clock component in case of an input optical signal in the case of an NRZ signal

4 is a graph showing a result of a simulation in which an eye opening penalty is converted into a power of a clock component in the case of an input optical signal in the case of an RZ signal

FIG. 5 is a schematic view showing the eye opening at the transmitting end and the eye opening at the measuring position in order to explain the eye opening penalty.

Description of the Related Art

100: clock component measuring device 110: photodetector

120: 1/2 bit delay device 130: differential amplifier

140: Narrow band filter 150: Power meter

200: Optical signal-to-noise ratio measuring apparatus 300: Error rate calculating apparatus

400: Optical amplifier (or optical network node)

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing an apparatus for measuring a signal error rate using the power of a clock component according to the present invention.

As shown in FIG. 1, an error rate measuring apparatus for an optical signal including a clock component measuring apparatus 100, an optical signal-to-noise ratio measuring apparatus 200, and an error rate calculating apparatus 300; And an optical amplifier (or optical network node) 400.

The optical signal-to-noise ratio measuring apparatus 200 measures the signal-to-noise ratio of the optical signal and the power of the optical signal using the optical signal-to-noise ratio measuring apparatus proposed in various methods.

A detailed configuration of the clock component measuring apparatus 100 for measuring a clock component of an optical signal includes a photodetector 110, a 1/2 bit delay unit 120, a differential amplifier 130, A narrowband filter 140, and a power meter 150. The principle of operation will be described below.

A part of the input optical signal is separated by the optical signal separator and most of the signal is sent to the optical amplifier 400 or the signal processing node of the optical communication network and a part thereof is transmitted to the clock component measuring apparatus 100 and the optical signal- ).

In this case, when the input optical signal is a non-return to zero (NRZ) signal which is the main type of optical communication at present, it must go through all the components of the clock component measuring apparatus 100 and the return to zero (RZ) signal, the 1/2 bit delay unit 120, the differential amplifier 130, the diodes D1 and D2, and the half-bit delay unit 120 after passing through the avalanche photodiode (APD) It is necessary to enter the narrowband filter 140 directly.

In the case of the RZ signal, the clock frequency component is directly passed through the narrowband filter 140 to extract the clock component. However, in the case of the NRZ signal, the clock frequency component does not exist and a non- I have to give it.

2A to 2F show the waveforms of the signals (A, B, C, D, E, and F) measured from the optical signal error rate measuring device when the input optical signal is an NRZ signal. It is easy to see how the clock components are formed.

The APD receiver, that is, the photodetector 11, which is the first part of the clock component measuring apparatus 100, serves to convert an optical signal into an electric signal. In the case of the NRZ signal, one of two identical data Bit delay so as to enter one of the inputs of the differential amplifier 130. The waveform graph at this time is shown in Fig. 2A (i.e., Fig. 1A) and Fig. 2B (i.e., Fig. 1B).

That is, when these signals are transmitted through the differential amplifier 130, the outputs corresponding to the signals A and B of FIG. 1 are outputted as one output C (waveform of FIG. 2C) The inverted output of this output (the waveform of Fig. 2 (d)) is output. When these outputs are combined after passing through the ultra-high frequency diodes D1 and D2, a waveform corresponding to Fig. 2E appears.

This is a waveform with a clock component. If you mark this waveform as a function, A (t) - A (t-T / 2) | . At this time, A (t) represents the waveform of the input signal, and T represents a period of 1 bit.

In this waveform, a narrowband filter 140 is used to extract only the clock frequency. The power meter 150 is connected to measure the power of the sinusoidal wave output through the narrowband filter 140. The magnitude of the power is measured and sent to the error rate calculation device 300, which is a function of the clock component measurement device 100.

Here, as an embodiment of the present invention, when the input optical signal is an NRZ signal, A process of extracting a clock component by implementing a function of A (t) - A (t-T / 2) will be described.

First, an input optical signal is divided by a power divider by a half, and one side is passed through a 1/2 bit delay device 120 to give a 1/2 bit delay. This creates A (t) and A (t-T / 2).

At this time, when they are put into two inputs of the differential amplifier 130 in order to be different from each other, A (t) - A (tT / 2) is outputted to one output C of the differential amplifier 130 shown in FIG. A (tT / 2) - A (t) is output to the other side. If they are connected to each other by a diode (D1, D2) over 0 V, A function of A (t) - A (t-T / 2) | is implemented as an electric circuit.

In another embodiment of the present invention, when the input optical signal is an NRZ signal, the following relationship is satisfied: | A (t) + A (t-T / 2) | It is needless to say that the clock component can be extracted by implementing the function of FIG.

In this case, after implementing A (t) + A (tT / 2), a function of filtering out only a portion of A (t) + A (tT / 2)> 0 via diodes Can be extracted.

The present invention, however, A (t) - A (t-T / 2) | The reason for this is that the clock component extracted by this method is the best way to convert the eye penalty.

The error rate calculation device 300 converts the eye opening penalty with the power of the clock frequency component and calculates the error rate of the input optical signal together with the measured value (optical signal-to-noise ratio, signal power) of the optical signal- . The formula for converting the eye opening penalty with the power of the clock component is derived from the empirical formula as follows.

1) In case of NRZ signal

Eye opening penalty

2) In case of RZ signal

Eye opening penalty

when, .

only, : The power of the clock component extracted from the optical signal

: The power of the clock component extracted from the transmitting end

At this time, if the power of the clock component is measured and a conversion formula different from the eye open penalty is used, information on chromatic dispersion of the optical fiber can be extracted or chromatic dispersion can be measured.

FIG. 3 is a graph showing a result of a simulation in which an input optical signal is converted into an eye open penalty with a power of a clock component in the case of an NRZ signal, FIG. 4 is a graph showing a simulation result in which an input optical signal is converted into an eye open penalty Fig.

3 and 4, a transmission rate of 10 GHz, an optical signal power of 0 dBm, and chromatic dispersion compensation at the node are assumed to be 90%. That is, in both cases, it is shown that the eye opening penalty can be accurately converted by the clock amplitude.

According to the simulation result of the present invention, even if the NRZ optical signal shown in FIG. 3 is changed in various conditions by only one expression expressed by Equation 1, the eye openness penalty can be converted with a small error.

Also, in the case of the RZ signal shown in FIG. 4, the eye opening penalty can be well calculated from the power of the clock component even in a single conversion formula. This calculation is performed in the error rate calculation device 300. [

The error rate calculation device 300 calculates the error rate from the eye opening penalty, the optical signal-to-noise ratio, and the power of the optical signal, as well as calculating the eye open penalty from the clock component. Generally, the error rate (BER) is expressed as follows.

In this case, erfc (x) = 1 - erf (x). erf (x) is an error function and is defined as follows.

At this time, Q in Equation (2) represents the quality of a signal as a Q parameter. This is expressed by the magnitude of the waveform and the magnitude of the noise, and the equation is as follows.

here, Can be expressed by the eye open penalty (expressed in dB scale), which is expressed by the following equation.

In Equation (4) Is the current value of the RMS noise at the 0 level and the RMS noise current value at the 1 level, which is expressed by the following equation. (1), the current amount Is (0) of the 0 signal, which is the current amount of the signal 1, which is the current amount of the signal 1, and the eye opening at the measurement position is shown in order to explain the eye opening penalty 5 is used.

here, Is the average amount of signal current, R is the reactivity of the receiver, The noise of the electric circuit, A preamplifier, The bandwidth of the optical amplifier, The bandwidth of the optical reception filter, The bandwidth of the electric circuit system, Is a spontaneous emission factor of the optical amplifier, and the carrier frequency v is determined depending on the type of the system.

When all these values are given, the eye penalty measured by the power of the clock is expressed by Equation 5 using the optical signal-to-noise ratio (OSNR) obtained by the optical signal-to-noise ratio measuring apparatus and the average power Ps of the signal, 6 to calculate the error rate (BER).

If the error rate is measured in the same manner as described above, the error rate due to the distortion of the signal that can not be measured with the optical signal-to-noise ratio can be accurately measured. In addition, the device also has a clock extraction function of the signal, and timing information due to the clock can also be obtained incidentally.

As described above, according to the method of measuring the error rate of a signal using the power of the clock component according to the present invention, the following advantages can be obtained.

First, the optical signal is converted into an electric signal in the optical transmission network node without the optical amplification repeater or the photoelectric / electro-optical conversion, and then the information about the error rate (BER) of the optical signal, which is known only through a lot of signal processing, It is easy to measure.

That is, this measurement method is a method of measuring the error rate which is the complete information on the quality of the signal, which is a remarkably improved method as compared with the conventional method of measuring only the optical signal-to-noise ratio.

Accordingly, it is possible not only to facilitate the operation / maintenance of the optical communication system and the optical transmission network using the optical amplifier, but also to contribute to the improvement of the reliability of such a system.

Second, the measurement method according to the present invention can be applied not only to an optical communication system but also to a general digital communication system.

Claims (6)

An optical signal error rate measuring device comprising a clock component measuring device, an optical signal-to-noise ratio measuring device, and an error rate calculating device; A method for measuring an error rate of an optical signal using an optical amplifier (or an optical network node) Extracting a clock component of the data from the input optical signal and measuring a clock size to convert the eye open penalty; Measuring an optical signal-to-noise ratio using a conventional optical signal-to-noise ratio measurement; And calculating an error rate of the optical signal using the measured eye opening penalty, optical signal-to-noise ratio, and optical signal intensity. 2. The method of claim 1, wherein when the input optical signal is an NRZ signal, a clock component is squared to generate a clock component, and then a narrowband filter (BPF) is used to extract a clock component. Of the error rate. 2. The method of claim 1, wherein when the input optical signal is an NRZ signal, A (t) - A (t-T / 2) (A (t): a waveform of an input optical signal, T: a period of 1 bit), and extracts a clock component. 2. The method of claim 1, wherein when the input optical signal is an NRZ signal, A (t) + A (t-T / 2) Wherein a clock component is extracted by implementing a function of a clock component. 2. The method of claim 1, wherein when the input optical signal is an NRZ signal, after implementing A (t) - A (tT / 2), only a portion of A (t) - A (tT / 2) And a clock component is extracted by using a clock function. 2. The method of claim 1, wherein, when the input optical signal is an NRZ signal, A (t) + A (tT / 2) And a clock component is extracted by using a clock function.