KR100948841B1 - Apparatus for clock extracting using circulator - Google Patents

Abstract

The present invention relates to an apparatus and method for recovering a clock using a circulator in an optical transmission system. The clock restoration apparatus proposed by the present invention includes a circulator for receiving and outputting N types of input data signals having different transmission speeds; A band pass filter for extracting each of N types of clock frequency components corresponding to transmission rates of each of N types of input data signals; and a clock amplifier for amplifying each of the N types of clock frequency components extracted; And a recovery device.

Optical Transmission System, Clock Recovery, Open Clock Extraction

Description

Apparatus for clock extracting using circulator}

The present invention relates to a clock recovery method and apparatus for electrically recovering a clock signal from a data signal received at a receiving side of an optical transmission system.

The present invention is derived from a study performed as part of the IT source technology development project of the Ministry of Information and Communication [Task Management Number: 2006-S-060-02, Task name: OTH-based 40G-class multi-service transmission technology development].

The receiving side of a general optical transmission system requires a clock extracting device or a clock restoring device for restoring a clock signal from a received data signal and supplying it to a data recovery block and a demultiplexing block. That is, generally, the receiving side of the optical transmission system recovers data and demultiplexes using the clock signal restored by the clock restoring apparatus.

However, the open clock restoring device using the passive filter has a disadvantage of being fixed and used only at one transmission rate. For example, at a 40 Gbit / s transmission rate, an STM-256 signal (39.81312 Gbit / s) multiplexed with four SDTM (Synchronous Digital Hierarchy) based STM-64 signals (9.95328 Gbit / s), and OTH ( There are a 42.8369 Gbit / s signal and an OTU-3 signal (43.018413 Gbit / s) multiplexed with four OTU-2 signals (10.709225 Gb / s) based on the Optical Transport Hierarchy. However, the conventional open clock restoring apparatus has no choice but to extract a clock signal corresponding to one of the three types of transmission rates.

Therefore, the conventional clock restoration apparatus has an inconvenience of replacing the band pass filter block in the clock restoration apparatus at the transmission speed or replacing the entire clock restoration apparatus whenever the transmission speed is changed.

The present invention has been proposed to solve the above-mentioned conventional problems. The present invention provides a method and apparatus for restoring each clock signal corresponding to each transmission rate in one clock restoration apparatus even when at least one or more data signals having different transmission rates are selectively input to the clock restoration apparatus. do.

Thus, a clock restoration apparatus capable of changing a transmission speed without replacing hardware is provided in an optical transmission system that supports various types of data transmissions having different transmission speeds.

According to the present invention, even when N types of data signals having different transmission speeds are selectively input to the clock restoring apparatus, additional hardware is not installed or changed by extracting clock signals corresponding to each transmission speed using a circulator and a band pass filter. It is possible to recover clocks for various baud rates in one open clock restorer.

The present invention provides an advantage of using an input data signal having a different transmission rate without changing the hardware structure. That is, the single clock restoration apparatus of the present invention can recover a clock signal corresponding to each transmission rate from two or more types of input data having different transmission rates.

In addition, the present invention is applicable to the above embodiment, it is possible to provide a clock signal corresponding to each transmission rate from the N type of data signals having different transmission rates in one clock recovery apparatus.

In a preferred embodiment of the present invention, an apparatus for restoring a clock using a circulator in an optical transmission system receives one input data signal of N types having different transmission speeds and cyclically outputs it in a single direction and outputs N output ports. And a N-type bandpass filter unit for filtering N-type passband center frequencies corresponding to each of the N-type transmission rates, wherein each bandpass filter unit is adapted to a transmission rate of the input data signal. When the corresponding clock frequency component corresponds to its passband center frequency, the input data signal is passed. Otherwise, the input data signal is reflected by the circulator.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings.

In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In addition, in order to be more faithful to the present invention, it is noted that changes or modifications can be made by those skilled in the art without departing from the spirit of the present invention.

1 and 2 show a clock restoring device (called a passive or open clock restoring device) using a conventional electrically passive filter.

1 illustrates a clock restoring apparatus for recovering a clock signal from a return to zero (RZ) type data signal including a clock frequency component corresponding to a transmission speed of a data signal, and FIG. 2 illustrates a clock frequency corresponding to a transmission speed. A clock restoring apparatus for restoring a clock signal from a non-return to zero (NRZ) type data signal that does not contain components.

The RZ clock restoring apparatus of FIG. 1 includes an electrical filtering unit 100 and a clock amplifier 110. The NRZ clock restoring apparatus of FIG. 2 includes a clock generator 200, an electrical filtering unit 210, and a clock amplifier 220.

The function of each component is as follows. First, the clock generator 200 generates a clock frequency component corresponding to the transmission speed of the data signal from the input NRZ data signal. In addition, the electrical filtering units 100 and 210 of FIGS. 1 and 2 filter only a specific clock frequency component from a signal having a clock frequency component. Thereafter, the clock amplifiers 110 and 220 amplify the clock signals output from the electrical filtering units 100 and 210.

The electrical filtering unit 100 or 210 may be a tank circuit using passive elements of a resistor (R), an inductor (L), and a capacitor (C) or a surface acoustic wave (SAW) when a data transmission rate is several Gbit / s or less. Implemented using filters, etc. On the other hand, it is difficult to fabricate tank circuits or SAW filters at transmission rates of several Gbit / s or more. Therefore, high Q-value dielectric resonator filters with excellent microwave characteristics are implemented.

In addition, the electrical filtering unit (100, 210) is manufactured to have a high Q value (= center frequency / 3-dB bandwidth) in order to obtain a high quality clock signal, where the high Q value is very narrow pass band of the filter This means that only certain frequency components can be extracted.

The center frequency of passive filters, such as the electrical filtering units 100 and 210, is usually fixed. Therefore, the clock restoring device using the passive filter has only a fixed transmission speed.

Therefore, hereinafter, a method and apparatus for providing each clock signal corresponding to each transmission rate in one clock restoration apparatus even when at least one or more data signals having different transmission rates are input to the clock restoration apparatus will be described. .

FIG. 3 illustrates a clock restoring apparatus for restoring a clock signal corresponding to each transmission rate from two types of RZ data signals having different transmission rates, according to an exemplary embodiment of the present invention.

The RZ clock restoring device uses a band pass filter having a center frequency corresponding to the transmission rate of each of the two types of RZ data signals, thereby selectively selecting a clock signal corresponding to each of the different transmission speeds through one clock restoration device. You can get

The circulator 300 receives one of two types of RZ data signals X1 and X2 having different transmission speeds, and circulates the same in one direction. Therefore, when the RZ data signal having the transmission rate X1 is input to the circulator 300, the X1 data signal is first output to the first output port 301, and has a passband center frequency corresponding to the transmission rate X1. The first clock signal corresponding to the transmission rate X1 is extracted by the first bandpass filter 310. The first clock amplifier 311 amplifies the extracted first clock signal.

On the other hand, when the RZ data signal having the transmission rate X2 is input to the circulator 300, the X2 data signal is first output to the first output port 301, but has a passband center frequency corresponding to the transmission rate X1. The light is reflected by the first band pass filter 310 and output to the second output port 302 of the circulator 300. Since the second band pass filter unit 320 has a pass band center frequency corresponding to the transmission rate X2, the second band pass filter unit 320 extracts a second clock signal corresponding to X2, and the second clock amplifier 321 extracts the second clock signal. Amplify the signal.

4 (a) to 4 (b) illustrate a clock restoring apparatus for restoring a clock signal corresponding to each transmission rate from two types of NRZ data signals having different transmission rates as an exemplary embodiment of the present invention. .

Since the clock frequency component is not included in the input NRZ data signal, the NRZ clock restoring apparatus of FIGS. 4A to 4B further includes a clock generator 410 unlike the RZ clock restoring apparatus of FIG.

The clock generator 410 converts the NRZ data signal into a signal including a clock frequency component when the electrical input signal is an NRZ data signal that does not include a clock frequency component.

Unlike the conventional clock generator 200 shown in FIG. 2, the clock generator 410 proposed in the present invention should be able to process each of the data signals having different transfer rates, and thus, input NRZ data having different transfer rates. A clock frequency component corresponding to each signal is generated.

Accordingly, the clock generator 410 shown in FIGS. 4A to 4B has clock frequency components corresponding to each of the two types of input signals when two types of NRZ data signals having different transmission rates are input. Create A process of generating the clock frequency component will be described in more detail with reference to FIG. 5.

In the case of the NRZ signal, the converted signal output from the clock generator 410 or the input data signal in the case of the RZ signal is applied to the circulators 300 and 400 as shown in FIGS. 3 and 4.

The circulators 300 and 400 cyclically output the signal including the input clock frequency component in one direction and sequentially so as to first output the first output ports 301 and 401. Therefore, when the period of the circulator input signal is T1, the signal output to the first output ports 301 and 401 includes clock frequency components X1 and Y1 corresponding to 1 / T1, and the period of the circulator input signal is T2 includes clock frequency components (X2, Y2) corresponding to 1 / T2.

The first output ports 301 and 401 of the circulator may include first and second band pass filter units 310 and 420 having a center frequency of 1 / T1 to extract clock frequency components X1 and Y1 corresponding to 1 / T1. Is connected to.

Therefore, if the period of the circulator input signal is T1, the clock frequency components X1 and Y1 corresponding to 1 / T1 are extracted from the first band pass filter unit 310 or 420, but if the period of the circulator input signal is T2, Clock frequency components X2 and Y2 corresponding to T2 are reflected from the first output ports 301 and 401 of the circulator and transmitted to the second output ports 302 and 402.

The second output ports 302 and 402 of the circulator are connected to the second band pass filter units 320 and 430 having the center frequency of 1 / T2, so that the clock frequency components X2 and Y2 corresponding to 1 / T2 are provided. The second band pass filter unit 302, 402 is extracted.

 More specifically, when a clock signal is extracted from a signal including a clock frequency component having a period T1 or T2 using the clock restoring apparatus of the present invention, the center frequency of the first band pass filter unit 310 or 420 may be used. Is 1 / T1, and the center frequency of the second band pass filter unit 320, 430 is 1 / T2, and the first band pass filter unit 310, 420, and the second band pass filter unit 320, 430 The narrower the passband and the higher the Q value, the clearer the clock signal is.

Each of the clock frequency components extracted by the first band pass filter unit 310 and 420 or the second band pass filter unit 320 and 430 may be a first clock amplifier 311 or 421 or a second clock amplifier 321. 431 is amplified and output. The first clock amplifiers 311 and 421 or the second clock amplifiers 321 and 431 may be implemented by any type of amplification device, but for integration, a monolithic microwave IC (MMIC) amplifier for integration. It is preferable to be implemented as.

 The clock amplifiers 311, 321, 421, and 431 amplify each clock signal to be suitable for the size of the final output signal, and may be maintained at a constant size even if the size of the data signal input to the clock restoring device changes within a certain range. Make sure Accordingly, it is preferable that the first clock amplifiers 311 and 421 and the second clock amplifiers 321 and 431 perform an amplification function only in regions of clock frequencies.

FIG. 5 is a diagram illustrating an internal configuration of the clock generation unit 410 of FIGS. 4A to 4B as a preferred embodiment of the present invention. Although the clock generation unit 410 of FIGS. 4A to 4B restricts the input NRZ data signal to two types having different transmission rates, the present invention is not limited thereto. A clock frequency component corresponding to each transmission rate may be generated from each of the NRZ data signals.

The clock generator 500 of FIG. 5 includes an input transmission line 510, a power divider 520, a first transmission line 530, a second transmission line 540, and an exclusive OR (EX-OR) logic element 550. And an output transmission line 560.

The input transmission line 510 transmits the input data signal to the power divider 520 by minimizing the transmission loss when NRZ data signals having different transmission speeds are respectively input.

The power divider 520 is composed of three identical resistors 520. An NRZ data signal having an arbitrary transmission rate (one of the N types of transmission rates) transmitted to the power divider is divided into two identical NRZ data signals through three resistors 520, and the same distributed data signals are divided into first, It is applied to two input ports of the exclusive OR (EX-OR) logic element 550 via two transmission lines 530 and 540, respectively.

As a specific example, the resistance value of the three resistors 520 constituting the power divider is a value obtained by dividing the characteristic impedance of the transmission line by three. That is, if the transmission line has a characteristic impedance of 50Ω, it is set to 16 ~ 17Ω. However, it should be noted that this is only an example and may be changed to the same or similar concept.

이다. 이를 위하여, 상기 제1,2 전송 선로(530,540)의 각 길이 L1과 L2는 아래의 수학식 1과 같이 설정된다. The first and second transmission lines 530 and 540 are for delaying the same NRZ data signal branched from the power divider 520 by different times. More specifically, the difference in delay time between two data signals is one of the average periods of two input NRZ signals so that clock frequency components corresponding to each transmission speed can be obtained from each of two types of NRZ data signals having different transmission speeds. / 2, expressed as a formula

to be. To this end, the lengths L1 and L2 of the first and second transmission lines 530 and 540 are set as in Equation 1 below.

Where L1 represents the length of the first transmission line 530, L2 represents the length of the second transmission line 540, c represents the luminous flux in free space, and ε _eff represents the dielectric constant of the substrate and the L1 and L2 transmission lines. It shows the effective permittivity determined by the structure. And T1 denotes a period of an input NRZ signal in which Y1 frequency components are generated, and T2 denotes a period of an input NRZ signal in which Y2 frequency components are generated.

Accordingly, the same two data signals transmitted to the two input ports of the exclusive OR (EX-OR) logic element 550 through the first and second transmission lines 530 and 540 are connected to the first and second transmission lines 530. According to the length difference of the 540 has a phase difference between each other. The exclusive OR (EX-OR) logic device 550 generates a clock frequency component corresponding to the transmission rate of the input NRZ signal by calculating an exclusive logical sum of two identical data signals having the phase difference. The output transmission line 560 transmits the output signal of the exclusive OR logic signal 550 including the clock frequency component to the circulator 400.

As another embodiment, the clock generator 500 may amplify the generated clock frequency component by inserting an amplifier at an output of the exclusive OR logic circuit 550. That is, when the size of the clock frequency component output from the exclusive OR (EX-OR) logic device 550 is small, amplification thereof may facilitate clock extraction even in circuit blocks after the clock generators 410 and 500. Can be.

Equation 2 indicates the length difference between the first and second transmission lines 530 and 540 for generating a clock frequency component corresponding to each transmission rate when N types of NRZ data signals having different transmission rates are input. . In this case, the circulator 400 is a 1: N circulator that cyclically outputs the circulator's input signal to N kinds of output ports, and operates N band pass filter units and N kinds of clock amplifiers. The frequency depends on the transmission speed of each of the N types of data signals.

L1; First transmission line length

L2; 2nd transmission line length

Tmax; Period of the data signal having the maximum transmission rate among N types of NRZ data signals having different transmission rates

Tmin; Period of the data signal having the minimum transmission rate among N types of NRZ data signals having different transmission rates

c; Speed of light in free space

ε _eff ; Effective permittivity determined by the permittivity of the substrate and the structure of the L1 and L2 transmission lines

6 shows a conceptual diagram of a clock restoring apparatus according to a preferred embodiment of the present invention.

In the optical transmission system, the clock restoring apparatus of the present invention recovers a clock by using a circulator. The clock restoring apparatus of the present invention inputs the circulator 610 and the circulator 610 to cyclically output N types of input data signals having different transmission speeds in a single direction. N types of clock frequencies extracted by the band pass filter 620 and the band pass filter 620 for extracting each of the N types of clock frequency components corresponding to the transmission rates of the N types of input data signals. And a clock amplifier 630 for amplifying each of the components.

7 shows a conceptual diagram of an NRZ clock restoring apparatus as a preferred embodiment of the present invention.

The NRZ clock restoring apparatus includes a clock generator 710 and a clock generated by the clock generator 710 for generating clock frequency components corresponding to respective transmission speeds from each of N types of NRZ input data signals having different transmission speeds. Circulator 720 for cyclically outputting signals containing frequency components to N output ports in a single direction, and N type bandpass filters for extracting clock frequency components corresponding to transmission rates of N types of input NRZ data signals. A unit 730, and N type clock amplification unit 740 for amplifying each of the extracted clock frequency components.

The N types of band pass filter units have different N types of passband center frequencies corresponding to each of the N types of transmission rates. Each band pass filter unit extracts a specific clock frequency component corresponding to the transmission rate of the input data signal when the input data signal corresponds to a specific passband center frequency assigned to the band pass filter. Reflect the input data signal.

delete

delete

The best embodiments have been disclosed in the drawings and specification above. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims.

Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 shows a clock restoring apparatus for extracting a clock signal from an RZ data signal of a single speed including a clock frequency component.

2 shows a clock restoring apparatus for extracting a clock signal from a single-rate NRZ data signal without a clock frequency component.

FIG. 3 illustrates a clock restoring apparatus for restoring clock signals corresponding to respective transmission rates from RZ data signals having different transmission rates, according to an embodiment of the present invention.

4A and 4B illustrate a clock restoring apparatus for restoring clock signals corresponding to respective transmission rates from NRZ data signals having different transmission rates, according to an exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating an internal configuration of the clock generation unit of FIGS. 4 (a) to 4 (b) as a preferred embodiment of the present invention.

6 shows a conceptual diagram of a clock restoring apparatus according to a preferred embodiment of the present invention.

7 shows a conceptual diagram of an NRZ clock restoring apparatus as a preferred embodiment of the present invention.

Claims (7)

An apparatus for recovering a clock using a circulator in an optical transmission system, A circulator having N output ports and cyclically outputting one input data signal of N types having different transmission speeds; and And N type band pass filter units for respectively filtering N types of pass band center frequencies corresponding to each of the N types of transmission rates, wherein each of the band pass filter units corresponds to a clock frequency component corresponding to the transmission rate of the input data signal. And passing the input data signal when the frequency corresponds to its own passband center frequency, and reflecting the input data signal to the circulator. The method of claim 1, wherein the input data signal is A clock restoring apparatus comprising: a RZ type signal comprising a clock frequency component. The method of claim 1, When the input data signal is an NRZ signal not including a clock frequency component, And a clock generator for generating each of N types of clock frequency components corresponding to transmission rates of the N types of input data signals. The method of claim 3, wherein And an output signal of the clock generator is used as the input data signal of the circulator. The clock generator of claim 3, wherein the clock generator And an N-type clock frequency component corresponding to each transmission rate from the N-type input data signals on the basis of an exclusive-OR operation. The method of claim 5, wherein the clock generation unit After receiving one type of data signal of the N types of input data signals and branching the same into two, the two branched signals are transmitted through the first transmission line and the second transmission line of different lengths, and then the exclusive logical sum. Perform the (EX-OR) operation, The difference in the branch signal propagation time between the first transmission line and the second transmission line is based on the Tmax which is the period of the NRZ data signal having the maximum transmission rate among the N types of input data signals that can be input and the NRZ data signal having the minimum transmission rate. Clock restoring device, characterized in that 1/2 of the average period between the period Tmin. The method of claim 1, And a clock amplifier configured to amplify each of the extracted N kinds of clock frequency components.

Images