KR20040003290A - Apparatus for protection switching of high speed ethernet equipment - Google Patents

Abstract

PURPOSE: A protection switching device of a high speed Ethernet device is provided to determine a threshold value of a 'Q' value in a system, and to decide whether the 'Q' value is less than certain performance, then to switch an optical switch, thereby quickly protecting the system. CONSTITUTION: A power level monitor(10) detects optical strength. A window level setup unit(20) detects the optical strength, and sets high and low levels of a window. A window monitor(30) compares the set window levels with a signal for detecting the optical strength, and detects whether the signal is included in the levels. A window error counter(40) counts window error signals, and transmits the error signals when an error rate exceeds a certain value. A switching controller outputs a switching control signal if one of optical strength detection signals is not a normal level. A switch(60) switches a protection optical line and an operational optical line.

Description

Apparatus for protection switching of high speed ethernet equipment

The present invention relates to a protection switching device and a method of a fast Ethernet device, and more particularly, to determine the performance of a fast Ethernet signal through a Q-factor monitoring, by which a signal having a performance below a certain level is received using the same. In this case, the present invention relates to a protection switching device and a method of a fast Ethernet device capable of guaranteeing transmission performance by switching an optical signal path.

Most SONET / SDH devices are used in the metro area and long distance area.

SONET / SDH device is a representative device for circuit switching and can communicate very stably due to the systematic network management function, but the packet is expensive and the packet is effectively multiplexed in case of IP traffic that is not continuous and bursty. There is a difficulty in transmitting. Therefore, in the macro area, communication service companies around the world have recently introduced Gigabit Ethernet devices in place of SONET / SDH devices, and are attempting to use them at very low cost.

Ethernet is the most widely installed local area network technology. Ethernet LANs typically use coaxial cables or special graded unshielded twisted pairs.

The most commonly installed Ethernet system is called 10BASE-T and provides a transmission rate of 10Mbps. All devices are connected by cable and competitively accessed using the CSMA / CD protocol.

Fast Ethernet and 100BASE-T provide up to 100Mbps and are commonly used as the backbone of local area networks to support workstations equipped with 100BASE_T cards.

Gigabit Ethernet, on the other hand, is about 1Gbps, supporting higher levels of backbone speed.

Due to the proliferation of the Internet, the capacity of Ethernet devices to handle packets effectively must also increase.

Most of the subscriber's high speed LANs are based on Ethernet, and because Ethernet devices are suitable for multiplexing these signals, 100 Mbps Fast Ethernet and 1 Gbps Gigabit Ethernet are rapidly being used. Standardization is underway at the IEEE 802.3 Committee.

However, Ethernet is a very efficient way to transmit packet data, but since it was basically a transmission equipment used in a private network of a company, it cannot guarantee transmission quality for a public service network of a communication service company which should guarantee 99.999% reliability. In case of an accident, the specification to be transferred within 50 msec cannot be satisfied.

In addition, the current communication network in the macro area uses a lot of annular networks due to the ease of protection switching. However, since the existing Ethernet devices are constructed based on the mesh network, fairness is used when connecting to the annular network. ) The problem becomes serious and protection switching takes a lot of time. In other words, when connected to the mesh network, it takes about 1 second to switch the protection of the Ethernet switch, while it takes about 30 seconds when the ring network is configured. This is because of the process of determining the rerouting method of the distributed discovery protocol (DP) called STP (Spanning Tree Protocol) used by Ethernet switches. Considering the characteristics of such an Ethernet device, the Ethernet device can be effectively used for the transmission of bursty data that is important for transmission efficiency, but it is difficult to use in combination with a conventional synchronous device. In other words, when Ethernet is used to increase the transmission capacity of Ethernet and require real-time transmission such as telephone and online broadcasting, Ethernet must greatly increase the signal quality when it is used in the macro area together with the existing synchronous device.

Methods used to improve the quality of Ethernet include Resilent Packet Ring (RPR) and Fiber Route Protection (FRP).

The RPR method is to implement a packet network that has a fast protection switching function and a performance monitoring function of the SONET network, and maximizes bandwidth utilization through spatial reuse, distributed fairness algorithm, and high speed. It aims to protect protection of the government. As a result, this method protects the system similarly to the existing SDH annular network, but it is slower than SDH, is a technology available only in the annular network, is not yet compatible with other companies' devices, and works with WDM devices. If used, there is a disadvantage that there must be a separate signal (signaling) to prevent the collision with the protection function of the WDM device.

In addition, FRP protects data by automatically switching between primary and secondary fibers in the event of an optical or network equipment accident. This method has the advantage of protecting regardless of the protocol of data to be transmitted because it is determined to be an accident when the received light intensity is smaller than the reference value. However, this method has a problem that cannot be discerned when the received optical signal is large but the SNR is bad and there are many errors. On the other hand, when Gigabit Ethernet is used in macro, the SNR of a signal is likely to be attenuated because it passes through multiple nodes because it has to pass through several nodes. Therefore, there is a problem that is difficult to apply to the macro area.

An object of the present invention for solving the above problems is to determine the performance of the fast Ethernet signal through a Q-factor, and transmits by switching the path of the optical signal only when a signal having a performance below a certain level is received using the same. To ensure performance.

1 is a graph analyzing a signal after converting a digital optical signal from a receiving end into a voltage;

2 is a graph showing a relationship between a signal distribution and a window level when k = 0.5.

3 is a graph showing the change in BER value according to the change in Pbw value for the case of K = 0.3 and K = 0.5.

4 is a block diagram illustrating a protection switching device for predicting a bit error rate (BER) of a digital signal according to the present invention.

5 is a circuit diagram illustrating a switching determining unit 50 of a protection switching device of a fast Ethernet device according to the present invention of FIG. 4.

<Description of Symbols for Major Parts of Drawings>

10: power level monitor

20: window level setup

21: mixer

22: Low Pass Filter (LPF)

23: Analog-Digital Converter (ADC)

24 microprocessor

25: Digital-Analog Converter (DAC)

30: window monitor

31, 32: comparator

33, 34: level detector

35: Clock Recovery

36: Limiting Amplifier

40: window error counter

50: switching decision unit

60: switch

PD: Photo Diode

AND: And gate

The protection switching device of the fast Ethernet device of the present invention for achieving the above object, the light intensity detecting means for detecting the light intensity;

Power level monitoring means for detecting a case where the level of the detection signal detected by the light intensity detection means falls below a reference value and outputting the light intensity detection signal;

Window level setup means for setting the high and low levels of the window by using the detection signal detected by the light intensity detecting means;

Window monitoring means for detecting whether the window level set by the window level setup means is included in the window level by comparing the detection signal of the light intensity detecting means;

Window error counter means for counting each time a window error signal is received from the window monitoring means and transmitting an error signal if the error rate exceeds a predetermined value;

Switching control means for outputting a switching control signal when any one of the error signal and the light intensity detection signal is not at a normal level; And

And switching means controlled by the switching control signal to switch between the operation light beam and the protection light path.

The above and other objects and features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a graph analyzing a signal after converting a digital optical signal from a receiver to a voltage.

Here, I ₀ is an average size of the space state, I ₁ is an average size of the bar state, and Id represents a threshold voltage for determining data.

The size of I _D to operate at the best performance is determined by Equation 1.

[Equation 1]

In addition, W _L and W _H are reference levels for determining signal performance, and the input NRZ signal is a reference value for setting a minimum size for obtaining a constant bit error rate (BER), and space and bar are Gaussian distribution. Assume that follows.

P (0/1) is the probability of judging the '1' signal to be '0', and P (1/0) is the probability of judging the '0' signal to be '1'. P (1/0) can be obtained by the following [Equation 2] and [Equation 3], respectively.

[Equation 2]

[Equation 3]

Here, since the signal distribution is Gaussian and the decay slope is large as the I _D value passes, the Id value is used instead of the infinity value to set an approximation value.

Therefore, BER can be calculated | required by [Equation 4] using the value calculated by [Equation 2] and [Equation 3].

[Equation 4]

Therefore, the probability Pb _W to be within the level among the received data values has a relationship as shown in [Equation 5] with Pb _L and Pb _H.

[Equation 5]

Therefore, when Pb _W is measured, Q value can be predicted by following [Equation 6].

[Equation 6]

Here, k value is calculated | required by [Equation 7].

[Equation 7]

The x value is obtained by Equation 8.

[Equation 8]

Where Z is the standard normal distribution.

Further, σ ₀ and σ ₁ are obtained by Equations 9 and 10, respectively.

[Equation 9]

[Equation 10]

Therefore, the BER value can be obtained by Equation 11 using the Q value obtained in Equation 6.

[Equation 11]

2 is a graph showing the relationship between the signal distribution and the window level when k = 0.5.

3 is a graph showing the change in the BER value according to the change in the Pbw value for the case of K = 0.3 and K = 0.5.

4 is a block diagram illustrating a protection switching device for predicting a bit error rate (BER) of a digital signal according to the present invention.

A photo diode (PD) converts and outputs an optical signal transmitted by an optical path to an electric signal ES.

The power level monitoring unit 10 measures the light intensity using the electric signal ES detected by the photodiode PD, detects a case where the light intensity falls below a reference value, and outputs the light intensity detection signal PM (Power mon).

Here, the sudden drop in the light intensity is a result of serious failures such as an accident of cutting a light beam or a failure of a light source. In such a case, switching should be performed at high speed regardless of signal performance.

The window level setup unit 20 receives the signal ES from the photodiode PD and sets the high and low levels of the window.

First, the signal ES detected by the photodiode PD removes the DC component and leaves only the AC component, and then is connected to two input terminals of the mixer 21, and then the output of the mixer 21 is connected to a low pass filter (LPF) ( Pass 22). Therefore, a value proportional to the square of Vpp can be detected as a DC voltage.

The signal passing through the low pass filter 22 is converted into a digital signal by an analog-to-digital converter (ADC) 23.

The signal converted into a digital signal is calculated by the microprocessor 24, and then converted into analog signals WH and WL by a digital-to-analog converter (DAC) 25, and then the window monitor unit 30 Is sent).

The window monitor 30 includes comparators 31 and 32 for comparing the set window levels WH, WL and the output ES of the photodiode PD, and level detectors 33 and 34 for detecting a signal included in the window level. And AND gate AND for outputting a logical combination of the output signals of the level detectors 33 and 34.

Therefore, the window monitor unit 30 outputs the window error signal WER when the output signal ES of the photodiode PD is not included in the window level set by the window level setup unit 20.

At this time, the signal detection timing is determined by the clock recovery circuit 35. Here, the clock recovery circuit 35 includes a limiting amplifier 36 that amplifies the output signal ES of the photodiode PD.

The window error counter 40 counts each time the window error signal WER is received from the window monitor 30, and then transmits an error signal QM when the error rate Pb _W exceeds a predetermined value. At this time, the error rate Pb _W can be calculated from the measurement time and the number of window errors. Therefore, Q-factor and BER can be calculated by the calculated error rate Pb _W.

The switching determination unit 50 outputs a signal SWC for switching the optical path when any one of the output PM and QM of the window error counter 40 and the power level monitor 10 is abnormal.

Switching the optical path is a case where the first light intensity is significantly lowered, and the second light intensity is large but noise is difficult to receive.

Here, the switching method is made non-recursive in order to use only one photodiode PD. That is, even if an accident is handled after being switched by one of the two causes mentioned above, it does not switch back to the original beam.

More cost is incurred because two photodiode PDs have to be used because both optical lines 61, 62 must be monitored simultaneously for working and protection.

FIG. 5 is a circuit diagram illustrating a switching determining unit 50 of a protection switching device of a fast Ethernet device according to the present invention of FIG. 4.

The output signal QM of the window error counter unit 40, which is the result of monitoring the Q-factor, and the output signal PM of the power level monitor unit 10, which is the result of monitoring the power, are D-flip flops 51, 52, respectively. Is applied to the input of the exclusive OR gate XOR.

Therefore, the exclusive oar gate XOR determines whether the outputs of the D-flip-flops 51 and 52 are the same to control the optical switch 60 for switching the operating light ray 61 to the protective light ray 62. Generate a control signal SWC.

When the Q-factor goes bad, that is, when QM (Q mon) goes high or the light intensity goes low, that is, when PM (Power mon) goes low, the input of the exclusive or gate XOR changes, The switching control signal SWC is enabled to switch the optical switch 60.

In the case of Ethernet signals, there is no supervisory overhead like a synchronous device, resulting in slower recovery time in the event of an accident. Therefore, in the present invention, the transmission performance is determined by searching the eye shape, and accordingly, a system for protecting and transferring the system is used.

The causes of the degradation of the optical signal include the cutting of the light path, damage to the light source for transmission, ASE noise of the optical amplifier, dispersion of the light path, and accident at the receiver. Most of these accidents detect the Q-factor by searching the eye shape. In order to determine the Q-factor, the signal size is divided into a number of sections, and a method of determining the total distribution using statistics obtained by comparing each section with the input signal is used. In the present invention, the exact Q-factor value cannot be calculated, but a method of protecting the system by determining whether the Q value is below a certain performance in a short time is used. Therefore, the present invention can be applied to an optical communication system that requires a fast changeover when an accident occurs.

As described above, since the window size and the signal detection probability and the Q value in the window are correlated, the system determines the threshold of the Q value and determines the size of the window. The system can be switched over by comparing the results and noting the desired Q value.

As described above, the protection switching device of the fast Ethernet device according to the present invention determines the threshold of the Q value in the system, determines whether the Q value is below a certain performance, and switches the optical switch in a short time by switching the optical switch. There is a protective effect.

In addition, a preferred embodiment of the present invention is for the purpose of illustration, those skilled in the art will be able to various modifications, changes, substitutions and additions through the spirit and scope of the appended claims, such modifications and changes are the following claims It should be seen as belonging to a range.

Claims (8)

Light intensity detecting means for detecting light intensity; Power level monitoring means for detecting a case where the level of the detection signal detected by the light intensity detection means falls below a reference value and outputting the light intensity detection signal; Window level setup means for setting the high and low levels of the window by using the detection signal detected by the light intensity detecting means; Window monitoring means for detecting whether the window level set by the window level setup means is included in the window level by comparing the detection signal of the light intensity detecting means; Window error counter means for counting each time a window error signal is received from the window monitoring means and transmitting an error signal if the error rate exceeds a predetermined value; Switching control means for outputting a switching control signal when any one of the error signal and the light intensity detection signal is not at a normal level; And And switching means controlled by the switching control signal to switch between an operation light beam and a protection light path. The method of claim 1, And said light intensity detecting means comprises a photodiode. The method of claim 1, The window level setup means, Analog to digital conversion means for converting the detection signal detected by the light intensity detection means into a digital signal; The digital signal includes a microprocessor for calculating a desired window level; And And a digital-to-analog converting means for converting the window level calculated by the microprocessor into an analog signal. The method of claim 3, wherein The window level setup means, A mixer in which only an AC component from which the DC component of the signal detected by the light intensity detecting means is removed is applied to two input terminals; And And a low pass filter for filtering the output of said mixer. The method of claim 1, The window monitoring means, A plurality of comparison means for comparing the window level set by the window level setup means with the level of the detection signal detected by the light intensity detection means; A plurality of level detecting means for detecting a signal included in the set window level; And And logic means for outputting the window error signal by combining the outputs of the plurality of level detecting means. The method of claim 5, wherein The window monitoring means, And a clock recovery means for determining a timing at which said plurality of level detecting means detects a signal. The method of claim 1, The switching control means, A first flip-flop to which the error signal is applied to a clock input terminal and an inverted output is fed back to a data input terminal; A second flip-flop to which the light intensity detection signal is applied to a clock input terminal and an inverted output is fed back to a data input terminal; And And logic means for exclusively summing the output of the first flip-flop and the output of the second flip-flop. The method of claim 1, The protection signal switching device of the fast Ethernet device, characterized in that the error signal is the result of monitoring the Q-factor.