KR20020048230A - Burst-Mode Optical Packet Tranceiver - Google Patents

Abstract

PURPOSE: A burst mode optical packet transceiver and a transmitting and receiving method are provided to transmits and receive a burst mode optical packet at a high speed by optically processing the transmission and receipt of data and clocks without using a CDR(Clock and Data Recovery) chip. CONSTITUTION: A burst mode optical packet transmitting and receiving unit(11) converts an inputted NRZ(Non Return-to-Zero) amplitude modulated digital electric signal into RZ(Return-to-Zero) amplitude modulated optical signals with two wavelength bands including data information and clock information, and adds the RZ amplitude modulated optical signals as one optical output. A burst mode optical packet receiving unit(12) recovers the NRZ amplitude modulated digital electric signal and the clock from the RZ amplitude modulated optical signal.

Description

Burst Mode Optical Packet Transceiver and Transmitting and Receiving Method {Burst-Mode Optical Packet Tranceiver}

The present invention relates to optical packet communication, and more particularly, to transmit and receive an optical packet in burst mode in an optical communication system such as ATM-PON, optical cable (Cable TV), etc., without using a preamble bit and using a CDR chip. An optical packet transceiver and a transmission and reception method capable of transmitting and receiving burst mode optical packets without use.

High speed optical packet communication is a very important technology for constructing the optical Internet including multimedia networks, and as the capacity of the optical network increases, the processing capacity of the optical packet required for optical transmission and optical connection technologies increases. The type of optical packet used in the optical network is generally a so-called burst mode type in which the amplitude of the received optical pulse is severely changed with time, the optical packet is transmitted asynchronously and has a time delay according to transmission. The receiving optical receiver is called a burst mode optical receiver.

Thus, an optical receiver for receiving an optical packet in burst mode form must be able to accommodate variations in signal strength and delay. In point-to-point communication, the signal fluctuations are slow enough to follow well with a general optical receiver, so the signal can be recovered only by the automatic gain control circuit and the clock extraction circuit. However, in burst mode communication such as optical packet communication and ATM-PON, signal intensity fluctuations and delay fluctuations are severe. This is because the transmission characteristics of the optical path are different for each optical packet to be transmitted.

In particular, in a communication system using short packets such as ATM, the optical receiver cannot be used because the time interval between the packets is too short. Accordingly, there is a need for the development of a burst mode optical transmission / reception method capable of recovering data and clocks within a short time regardless of signal strength or delay variation of transmitted optical packets.

So far, the following methods have been attempted to receive high speed optical packets. (1) When idle time occurs without optical packets being transmitted, data of "1" and "0" are randomly inserted. A method of configuring a frame for synchronization of transmission / reception periods, (2) a method of configuring an optical receiver to enable burst mode reception, and (3) a method of configuring an optical transmitter to enable burst mode transmission and reception There are three categories.

In the case of (1), since unnecessary optical packets without information are transmitted, the transmission efficiency of the optical network is reduced. Next, in the case of (2), the information on the packet and the packet signal size is determined within the first pulse width of the incoming signal, and the value of the data discrimination circuit is set to this value. and a method for synchronizing the preamble instantaneously in the clock extraction circuit and generating a data payload using the synchronized clock. In the case of (3), the signal intensity and phase of the optical signal output from the optical transmitter are adjusted to reach the optical receiver with an optical signal having a constant signal strength and time delay.

On the other hand, Korean Patent No. 249816 discloses a burst mode optical receiver capable of reducing the penalty of 1.5 dB caused by receiving a burst mode signal without using a preamble bit, and the input signal is divided into two through an optocoupler. Each is then amplified by a preamplifier with a different bandwidth, and by adjusting the bandwidth ratio between the two preamplifiers, the penalty for burst mode reception can be reduced to 0.5 dB or less.

However, the present invention relates to an optical packet receiver, which is composed of an optical transmitter and an optical receiver as a pair as described below, and transmits clock information and data together in an optical transmitter and recovers each of the optical receiver. There is a difference.

Currently, some commercially available burst-mode receivers sell 155Mbps / 622Mbps optical receivers, but their operation is not good, and some laboratories announce successful 1Gbps burst mode optical signal reception. If a signal capacity of several tens of Tbps or more is to be processed in one node of the optical network, the signal rate of the optical packet should be tens of Gbps or more. Rather than electrically processing the transmission and reception of burst mode signals, it is possible to speed up the burst mode optical packet signal. The clock and data recovery (CDR) chip used in the conventional optical receiver is an electrical method of extracting a clock, and there are many difficulties in speeding up.

In the present invention, a function of extracting a clock from the first pulse received and recovering data without using a conventional clock data recovery (CDR) chip, which has been limited in speeding up a burst mode optical packet signal, and receiving optical An object of the present invention is to provide a burst mode optical packet transceiver and a transmission / reception method having a function of recovering data regardless of a change in amplitude of a signal.

1A is a structural diagram of a burst mode optical packet transceiver according to an embodiment of the present invention;

FIG. 1B is a specific first structural diagram of the optical signal output means of FIG. 1A;

FIG. 1C is a detailed second structural diagram of the optical signal output means of FIG. 1A;

2 is a transmission flowchart of a transmitter of the optical packet transceiver of FIG. 1;

3 is a flowchart illustrating a receiving unit of the optical packet transceiver of FIG. 1;

4 is an NRZ-RZ converter and a conversion signal processing flowchart used in a transmission unit of the optical packet transceiver of FIG.

5 is a signal discriminator and signal discrimination flowchart used in a receiver of the optical packet transceiver of FIG.

* Explanation of symbols for the main parts of the drawings

11: burst mode optical packet transmitter 110: optical signal output means

111: Inverter / Buffer

112a, 112b: nonreturn-to-zero (NRZ) to return-to-zero (RZ) converters

113a, 113b: Light emitting device 12: Burst mode optical packet receiver

116: wavelength selection means 117: wavelength variable optical signal generating means

122a, 122b: light receiving element

According to the first aspect of the present invention, a burst mode optical packet that makes an input NRZ amplitude modulated digital electrical signal into an RZ amplitude modulated optical signal in two wavelength bands including data information and clock information, and adds them together into one optical output. A transmitter 11; And a burst mode optical packet receiver 12 for recovering an NRZ amplitude modulated digital electrical signal and a clock from the RZ amplitude modulated optical signal.

In addition, according to the second aspect of the present invention, the burst mode of making the input NRZ amplitude modulated digital electrical signal into an RZ amplitude modulated optical signal in two wavelength bands including data information and clock information, and then adding them together into one optical output. Optical packet transmission step; And a burst mode optical packet receiving step of recovering an NRZ amplitude modulated digital electrical signal and a clock from the RZ amplitude modulated optical signal.

Reference will now be made in detail to the preferred embodiments of the present invention, by way of example only, with reference to the accompanying drawings.

First, referring to FIG. 1A, a suitable embodiment of a burst mode optical packet transceiver according to the present invention is shown. The transceiver is largely comprised of an optical transmitter 11 and an optical receiver 12, and the optical transmitter 11 ) Is composed of an inverter / buffer 111, NRZ-RZ converters 112a and 112b, and an optical signal output means 110.

The inverter is a device for reversing the pulse pattern of the input electrical signal, the buffer is a device used to compensate for the time required in the inverter, and transmits the electrical signal with a certain time delay. The NRZ-RZ converters 112a and 112b are devices for converting NRZ pulses into RZ pulses. In addition, the optical signal output means 110 receives the output of the NRZ-RZ converter to generate an output optical signal.

Detailed structure diagrams of the optical signal output means 110 are shown in FIGS. 1B and 1C. First, referring to FIG. 1B, the optical signal output means 110 generates a laser diode 113a for generating information-bearing light. 113b) and an optical combiner 114 for combining the two optical signals and outputting one optical signal.

The optical packet transmission procedure performed by the optical transmitter 11 configured as shown in FIG. 1B will now be described with reference to FIG. 2.

(1) The input of the optical transmitter is input to the inverter / buffer 111 in the form of NRZ amplitude modulated digital data. For example, assume that digital data of '01001010011' is input. One digital data passes through an inverter to generate a pulse in which the pattern of the pulse is inverted (22). Another digital data goes through the buffer (21). Here, the buffer is used to equalize the propagation time of the two electrical signals.

(2) The two signals output from the inverter / buffer 111 are input to NRZ-RZ converters 112a and 112b, respectively, and are converted into RZ amplitude modulated digital data. That is, NRZ data denoted by "21" of FIG. 2 is converted into RZ data denoted by "23", and NRZ data denoted by "22" in FIG. 2 is converted into RZ data denoted by "24". This NRZ-RZ conversion can be obtained by synchronizing the AND operation by synchronizing the NRZ digital data 41 and the clock 42 which is twice the data frequency using an AND gate as shown in FIG.

(3) The laser diodes may be modulated with the RZ amplitude modulated electrical signals, respectively, to generate two RZ amplitude modulated optical signals. However, two laser diodes generate optical signals in different wavelength bands.

(4) Next, two RZ amplitude modulated optical signals are combined in an optical combiner and output as one output (25). The optical combiner is connected to an optical fiber for transmission.

On the other hand, since the optical transmitter 11 configured as shown in FIG. 1C differs from only a specific configuration of the optical signal output means 110, but the other configuration is the same as that of FIG. 1B, a signal processing procedure for the portion of the optical signal output means 110 is provided. Looking at it as follows.

The RZ amplitude modulated electrical signals are combined in the electric combiner 115 to modulate the wavelength tunable laser diode 117. At the same time, the RZ amplitude modulated electrical signals determine the operating wavelength of the wavelength tunable laser diode 117 by the wavelength selecting means 116. That is, in the time interval in which the upper RZ amplitude modulated electrical signal 112a operates at, for example, "1", the wavelength tunable laser diode 117 operates at wavelength "1" and the lower RZ amplitude modulation. For example, the wavelength variable laser diode 117 operates at wavelength "2" and outputs signals of two wavelengths during the time period during which the electrical signal 112b is operated at "1".

The RZ amplitude modulated optical signal transmitted through the optical fiber is restored to the NRZ amplitude modulated digital data by the optical receiver 12.

The optical receiver 12 includes an optical splitter 121, photodiodes 122a and 122b, a differential amplifier 123, a clock generator 124, and a signal discriminator 125. The optical splitter 121 separates the optical signal for each wavelength from the incident optical signal, the photodiodes 122a and 122b convert the incident optical signal into an electrical signal, and the differential amplifier 123 inputs two electrical signals. Amplifying the difference, clock generator 124 generates a clock from the output of differential amplifier 123. The signal discriminator 125 recovers data using a clock from the output of the differential amplifier 123.

The optical packet recovery procedure performed by the optical receiver 12 will now be described with reference to FIG. 3.

(1) The input of the optical receiver is a form 31 in which the RZ amplitude modulated optical signals are mixed in two wavelength bands, and are incident on the optical splitter and separated into two optical signals for each wavelength.

(2) The two separated optical signals are incident on the photodiodes 122a and 122b, respectively, and are converted into electrical signals (32 and 33). However, the electrical signal denoted by reference numeral "32" in FIG. 3 is the electrical signal denoted by reference numeral "23" in FIG. 2, and the electrical signal denoted by reference numeral "33" in FIG. Correspond to each electrical signal marked with "."

(3) The two electrical signals output from the photodiodes 122a and 122b are excited as inputs to the differential amplifier 123, and the difference between the two electrical signals is amplified and output. At this time, the electric signal has a form in which pulses are crossed positively and negatively as shown by reference numeral "34". The electrical signal output from the differential amplifier 123 is excited to the input of the signal discriminator 125 and the clock generator 124. The differential amplifier 123 always maintains the discrimination reference point of "0" and "1" at zero at signal discrimination.

(4) The clock generator 124 is a device that takes an absolute value of an electrical signal that is crossed positively and negatively, and converts a negative signal into a positive signal having the same absolute value. At this time, the electrical signal is used as a clock when recovering data in a form in which pulses exist at regular intervals, as shown by reference numeral 35. In addition, since the clock is generated from the first input of the clock generator 124, a separate preamble is not required.

(5) The signal discriminator 125 recovers the input signal using the output signal from the differential amplifier 123 and the clock generated by the clock generator 124 to NRZ amplitude modulated data (36). As a suitable device of the signal discriminator 125 used in the burst mode optical packet transceiver according to the present invention, as shown in FIG. 5, a D flip-flop may be used. The recovered data is an NRZ amplitude modulated electrical signal, which is the same as '01001010011' as the input of the optical transmitter.

In the burst mode optical packet optical transmitter according to the present invention, the optical transmitter transmits only an amplitude modulated signal and recovers burst mode data and a clock by using a CDR chip in the optical receiver. It generates and transmits a signal containing a clock and a clock and recovers the data and clock from the optical receiver. At this time, the transmitted optical signal consists of two wavelengths.

By eliminating the existing CDR chip, which is a major factor in rate limiting in burst mode optical packet transmission and reception, high speed burst mode optical packet transmission and reception is possible. In addition, the data recovery can be performed regardless of the amplitude change of the received optical signal. In addition, since the preamble used for the recovery of the clock is not required in the conventional burst mode communication, an efficient packet frame can be configured.

The description so far is directed to the preferred embodiments for the understanding of the invention, and the invention is not limited thereto, and those of ordinary skill in the art do not depart from the scope and spirit of the appended claims. It is obvious that various modifications and variations can be made without departing from the spirit of the invention.

As described above, according to the burst mode optical packet transceiver according to the present invention, by optically processing data and clock transmission and reception without using a conventional CDR chip which has been limited in speeding up the speed of the burst mode optical packet signal. Can transmit and receive burst mode optical packets at high speed. In addition, data can be recovered regardless of the amplitude change of the received optical signal, and the clock and data can be recovered from the first arriving pulse without a separate preamble, thereby forming an efficient packet frame.

Claims (13)

A burst mode optical packet transmitter 11 configured to generate an input NRZ amplitude modulated digital electric signal into an RZ amplitude modulated optical signal including data information and clock information, and then add the combined NRZ amplitude into one optical output; And A burst mode optical packet transceiver comprising: a burst mode optical packet receiver (12) for recovering an NRZ amplitude modulated digital electrical signal and a clock from an RZ amplitude modulated optical signal. The method of claim 1, The transmitter 11 is: An inverter / buffer means (111) for reversing the pulse pattern of the input electric signal and passing the input electric signal with a predetermined time delay; A pair of NRZ-RZ converting means (112a, 112b) for converting the NRZ pulses output from the interleaver / buffer means into RZ pulses, respectively; And Burst mode optical packet transceiver characterized in that it comprises an optical signal output means (110) for receiving each of the RZ signals output from the NRZ-RZ conversion means and outputs two optical signals of different predetermined wavelengths. The method of claim 2, The optical signal output means 110: Optical signal generating means (113a, 113b) receiving outputs from the pair of NRZ-RZ converting means (112a, 112b) and generating two optical signals having different constant wavelength bands; And A burst mode optical packet transceiver comprising: an optical coupling means (114) for adding the output optical signals of each of the optical signal generating means and outputting them to one output. The method of claim 2, The optical signal output means 110: Signal combining means (115) for adding the outputs from the pair of NRZ-RZ conversion means (112a, 112b); Wavelength selecting means (116) for selecting an output wavelength of the optical signal generating means (117) in accordance with the output from the pair of NRZ-RZ converting means (112a, 112b); And Burst characterized in that it is composed of a wavelength-variable optical signal generating means 117 for receiving the output signal of the signal combining means 115 and outputs an optical signal having a different wavelength in accordance with the output signal of the wavelength selection means 116 Mode optical packet transceiver. The method of claim 1, The receiver 125 is: Optical splitting means 121 for separating the optical signal for each wavelength from the incident optical signal; A pair of light converting means (122a, 122b) for receiving the output optical signal of the light splitting means and converting them into electric signals; Differential amplification means (123) for amplifying the magnitude difference of the output electrical signal from the optical conversion means; Clock generation means (124) for generating a clock of twice the frequency of the input signal frequency used for data recovery by taking an absolute value of the output signal of the differential amplification means (123); Burst mode optical packet transceiver characterized in that it comprises a signal discriminating means (125) for recovering data from the output of the clock generating means (124) and the differential amplification means (123). The method of claim 3, wherein Burst mode optical packet transceiver, characterized in that each of the optical signal generating means is composed of a laser diode. The method of claim 4, wherein The wavelength tunable optical signal generating unit 117 converts an NRZ amplitude modulated digital electric signal into an RZ amplitude modulated optical signal having two wavelengths having different operating wavelengths according to " 1 " and " 0 " Burst mode optical packet transceiver, characterized in that consisting of. The method according to claim 3 or 4, The pair of NRZ-RZ converting means 112a and 112b respectively have an input NRZ digital electrical signal 41 having a frequency f and a clock 42 having a frequency 2f as input signals, and an RZ digital electrical signal 43 Burst mode optical packet transceiver, characterized in that consisting of two input-AND gate for outputting. The method of claim 5, The pair of optical conversion means (112a, 112b) is a burst mode optical packet transceiver, characterized in that each consisting of a photodiode. The method of claim 5, The signal discrimination means (125) is a burst mode optical packet transceiver, characterized in that consisting of a flip-flop. A burst mode optical packet transmitting step of making an input NRZ amplitude modulated digital electric signal into an RZ amplitude modulated optical signal including data information and clock information, and then adding them together as one optical output; And A burst mode optical packet transmission / reception method comprising a burst mode optical packet receiving step of recovering an NRZ amplitude modulated digital electrical signal and a clock from an RZ amplitude modulated optical signal. The method of claim 11, The optical packet transmission step: A first step of receiving an NRZ amplitude modulated electrical signal and outputting a first signal having a reversed pulse pattern and a second signal delaying the electrical signal by a predetermined time; A second step of converting the first signal and the second signal into RZ pulses, respectively; A third step of generating two output signals in the second step as optical signals having different predetermined wavelength bands; And And a fourth step of adding the two output signals in the third step and outputting them as one optical signal. The method of claim 11, The optical packet receiving step is: A fifth step of separating the optical signal for each wavelength from the input optical signal and outputting third and fourth signals; A sixth step of converting the third and fourth signals into electrical signals, respectively; A seventh step of amplifying the magnitude difference of the output electrical signal in the sixth step; An eighth step of generating a clock from the output in the seventh step; And And a ninth step of recovering and outputting data from the outputs of the seventh and eighth steps.