KR20100061266A - Olt system for configuring tdma-pon and continuous mode receiver of the olt system - Google Patents

Abstract

PURPOSE: An OLT(Optical Line Terminal) system for configuring a TDMA-PON and a continuous mode receiver of the OLT system are provided to achieve high speed TDMA communication by configuring an uplink of a TDMA-PON with an ONU/ONT having an OLT and a burst mode transmitter. CONSTITUTION: A continuous mode receiver includes signal processing devices for continuous mode(410,420,430) and a timing unit(440). The continuous mode receiver restores a clock and data from a burst signal which is up-transmitted from an optical network terminal. In order for a clock data recovery circuit, which is the continuous mode signal processing device, to maintain a normal state, the timing unit provides a timing pattern.

Description

OLT system for configuring TDMA-PON and continuous mode receiver of the OLT system constituting a passive optical subscriber network of time division multiple access method

The present invention relates to a passive optical subscriber network system of a time division multiple access method, and more particularly, to an optical line terminal (OLT) constituting a passive optical subscriber network system.

This study was derived from the research conducted as part of the original technology development project of the Ministry of Knowledge Economy and the Korea Institute of Information and Telecommunications Promotion. [Task name: FTTH Service Development Experiment Project]

Recently, the installation of the FTTH (Fiber to the Home) network is proceeding at high speed. When the FTTH network is divided into technical methods, it is classified into three types: AON (Active Optical Network), TDMA-PON (Time Division Multiple Access-Passive Optical Network), and WDM-PON (Wavelength Division Multiplexing-Passive Optical Network). TDMA-PON among these three FTTH networks will be discussed.

The key components of TDMA-PON are optical line terminals, passive optical distribution networks, optical network termination devices (Optical Network Terminals (ONTs) or Optical Network Units (ONUs)). TDMA-PON's downlink (OLT transmission, ONU / ONT reception) consists of continuous mode transceiver, and uplink (ONU / ONT transmission, OLT reception) consists of burst mode transceiver. It is.

Since TDMA-PON is configured in the form of point to multi-point (P2MP) via an optical power splitter, the physical distance from the OLT to the ONU / ONTs is at each ONU / ONT location. There is no other choice. As a result, the transmission delay time and the transmission path loss of the optical signal differ depending on the position of the ONU / ONT. Therefore, the receiver of the OLT should be able to communicate regardless of the transmission delay time and transmission path loss of the optical signal according to the position of the ONU / ONT.

However, when comparing the continuous mode receiver and the burst mode receiver of the same speed, the continuous mode receiver has a narrow dynamic range. In addition, a very long time is required to recover the clock and data from signals with high transmission delay. Due to this problem of continuous mode receivers, current TDMA-PON OLT has a burst mode receiver.

On the other hand, TDMA-PON currently in operation is divided into GE-PON (Gigabit Ethernet-PON) and G-PON (Gigabit capable PON) according to the protocol. In the case of GE-PON, the uplink transmission rate and the downlink transmission rate are the same as 1.25Gbps. In the case of G-PON, the maximum transmission rate of the uplink is 2.5 Gbps, and the maximum transmission rate of the downlink is 1.25 Gbps.

Standardization organizations such as IEEE and FSAN are actively standardizing GE-PON and G-PON systems that provide uplink / downlink transmission speeds of 10Gbps with the goal of launching commercial systems in two or three years. In both GE-PON and G-PON, since downlink is composed of a continuous mode transceiver, there is no problem in increasing the transmission speed. However, since the uplink is composed of a burst mode transceiver, there is a problem in increasing the transmission rate. Currently, 10Gbps high-speed continuous mode transceiver has been developed and applied to metro network or long-distance transmission network system, but high speed burst mode transceiver of 2.5Gbps or more is under development. Especially in the case of high speed burst mode receivers, the speed of technology development is not fast. Since the 155Mbps or 622Mbps Burst Mode receivers were commercialized in the early 2000s, the 1.25Gbps Burst Mode receivers have been commercialized and operated as of 2008.

An object of the present invention is to enable high-speed time division multiple access communication by configuring an uplink of a TDMA-PON with an OLT having a high speed continuous mode receiver and an ONU / ONT having a burst mode transmitter.

In order to solve the above technical problem, the OLT is a signal processing element for continuous mode for recovering clock and data from a burst signal transmitted upward from ONU / ONT, and clock data, which is a signal processing element for continuous mode. And a continuous mode receiver including a timing unit providing a timing pattern so that clock data recovery can be maintained in a normal state.

According to an aspect of the present invention, the timing unit supplies the first timing pattern to the clock data recovery circuit so that the clock data recovery circuit transitions from an initial state to a normal state in the step of turning on the OLT.

According to an aspect of the present invention, the timing unit supplies a second timing pattern to the clock data recovery circuit so that the clock data recovery circuit remains in a normal state during the discovery process of the OLT.

According to an aspect of the present invention, the timing unit is configured to maintain the normal state of the clock data recovery circuit in a time interval in which the bandwidth is not allocated to the registered ONUs / ONTs while the OLT is in communication with the registered ONUs / ONTs. The timing pattern is supplied to the clock data recovery circuit.

On the other hand, continuous mode receiver for receiving a burst mode optical signal transmitted from the ONU / ONT in the TDMA-PON OLT for solving the above-described technical problem, the optical detector for receiving the optical signal and convert it into an electrical signal; A transimpedance amplifier for amplifying the converted electrical signal; A limiting amplifier for amplifying the electrical signal amplified by the transimpedance amplifier; A clock data recovery circuit for recovering clock and data from the signal amplified by the limiting amplifier; And a timing unit providing a timing pattern so that the clock data recovery circuit can maintain a normal state.

By adding Timing Unit to general continuous mode receiver structure, it can receive burst signal of ONU / ONT by continuously providing received signal so that clock data recovery circuit of continuous mode receiver can maintain normal state without transitioning to initial state. Make sure Therefore, the uplink of the TDMA-PON can be configured with an OLT having a high speed continuous mode receiver and an ONU / ONT having a burst mode transmitter, thereby enabling high-speed time division multiple access communication. In addition, the implementation of the OLT optical receiver as a continuous mode receiver creates the additional effect of lowering the OLT price compared to the OLT having a burst mode receiver.

The foregoing and further aspects of the present invention will become more apparent through the preferred embodiments described with reference to the accompanying drawings. Hereinafter, the present invention will be described in detail to enable those skilled in the art to easily understand and reproduce the present invention.

1 is a configuration diagram of a conventional TDMA-PON.

The TDMA-PON is largely composed of an OLT 100, a remote node = optical power splitter (RN) 110, and an ONU / ONT 120. The OLT 100 has a burst mode receiver (BM-RX) 101 and a continuous mode transmitter (CM-TX) 102, and the ONU / ONT 120 has a burst mode transmitter (BM-RX) 101. a burst mode transmitter (BM-TX) 121 and a continuous mode receiver (CM-RX) 122.

2 is a configuration diagram of a TDMA-PON according to an embodiment of the present invention.

The entire configuration is composed of an OLT 200, a remote node (RN) 210, and an ONU / ONT 220 similarly to the TDMA-PON configuration of FIG. 1. The OLT 200 has a continuous mode receiver (CM-RX) 201 and a continuous mode transmitter (CM-TX) 202, the ONU / ONT 220 is a burst mode transmitter ( a burst mode transmitter (BM-TX) 121 and a continuous mode receiver (CM-RX) 122. Compared to FIG. 1, the difference in hardware configuration of the TDMA-PON is that the OLT 100 of FIG. 1 is configured as a burst mode receiver for uplink, whereas the OLT 200 of FIG. 2 is configured for uplink. It consists of a continuous mode receiver.

3 is a block diagram of a typical continuous mode receiver.

The continuous mode receiver includes a photodetector (PD) 300, a transimpedance amplifier (TIA) 310, a limiting amplifier (LA) 320, and a clock data recovery circuit. , CDR) 330. TIA 310, LA 320, and CDR 330 are signal processing elements for CM. The TIA 310 converts and amplifies the current signal converted by the PD 300 into a voltage signal. The LA 320 amplifies the voltage signal received from the TIA 310 to make a signal having a constant output level and transmits the signal to the CDR 330. That is, the LA 320 outputs an appropriate voltage level so that the CDR 330 can recognize it as a 0 or 1 signal. The CDR 330 then recovers the data and clock from the signal output from the LA 320.

The general continuous mode receiver illustrated in FIG. 3 is suitable for receiving an optical continuous signal and is not suitable for receiving an optical burst signal. Since the continuous mode receiver 201 of the OLT 200 of FIG. 2 should receive a burst optical signal transmitted upward from the burst mode transmitter 221 of the ONU / ONT 220, the general continuous mode as illustrated in FIG. 3. If implemented as a receiver, it cannot process the received signal normally.

The reason why the normal signal processing is not possible is that the CM signal processing elements transition from the initial state to the normal state only when the signal is received for a certain time unlike the BM signal processing elements due to their characteristics. Here, the initial state means a state in which normal operation cannot be performed, and the normal state means a state in which normal operation can be performed. In the typical continuous mode receiver as shown in FIG. 2, when there is no reception signal for a predetermined time, the CDR loses synchronization information and transitions from the normal state to the initial state. It takes a long time to pay. Therefore, a typical continuous mode receiver cannot process a burst signal normally.

4 is a block diagram of a continuous mode receiver 201 constituting the OLT of FIG. 2 according to an embodiment of the present invention.

The continuous mode receiver 201 includes a PD 400, a TIA 410, an LA 420, a CDR 430, and a timing unit 440. The PD 400, TIA 410, LA 420, CDR 430 configurations are the same as the PD 300, TIA 310, LA 320, and CDR 330 configurations of FIG. 3. However, the output signal of the TIA 410 is combined with the output signal of the Timing Unit 440 and input to the CDR 430. The timing unit 440 receives the control signal and the clock signal CLK from the control unit of the OLT 200, generates timing patterns, and provides the timing patterns to the CDR 430.

5 is an exemplary diagram of timing patterns generated by the timing unit 440 of FIG. 4.

-First timing pattern (IDLE Pattern): When the OLT is powered on, the timing unit 440 generates and outputs a pattern, and '1' and '0' are repeated during T _p . Since there is no activated ONU / ONT at the stage when the OLT is powered on, there is no optical signal received by the PD 400. Accordingly, the CDR 430 transitions from the initial state to the normal state by receiving the IDLE pattern provided by the Timing Unit 440.

DISCOVERY PATTERN: A discovery process must be performed to register a newly powered ONU / ONT on the network. The discovery process refers to a process of registering a new ONU / ONT with a passive optical network in a network. The OLT may perform the discovery process periodically to detect the presence or absence of a new ONU / ONT or at any moment according to a system operator's command. However, if there are ONU / ONTs that are IN-SERVICE in order for the OLT to perform the discovery process, they must stop transmitting data. Since the new ONU / ONT has not been allocated bandwidth for uplink, if the ONU / ONT in service continues to transmit even during the discovery processor, it may collide with the message of the new ONU / ONT. Therefore, when the OLT performs the discovery process, if there is no newly powered-on ONU / ONT, no optical signal is transmitted on the uplink. In this case, the OLT continuous mode receiver loses synchronization information and transitions from the normal state to the initial state due to the absence of the input signal.

In order to prevent this, the CDR 430 of the continuous mode receiver 201 may maintain the normal state without transitioning to the initial state by receiving the DISCOVERY Pattern provided by the Timing Unit 440. In one embodiment, the DISCOVERY Pattern sets the “1010 ...” bit string to T _1. Lasts for ₂ seconds and the “0000 ...” bit string By repeating for a period of time (T ₁ + T ₂ ), data loss due to the overlap of the DISCOVERY Pattern and the message transmitted by the newly powered ONU / ONT can be minimized.

3rd Timing Pattern (IN-SERVICE Pattern): The timing pattern provided by the Timing Unit 440 to the CDR 430 while the OLT communicates with registered ONU / ONTs in a time division multiple access manner. Registered ONUs / ONTs are allocated their respective time-sharing bandwidths from the OLT to communicate with each other over uplink without conflict. However, since there is no optical signal in the section where the bandwidth is not allocated, the continuous mode receiver 201 of the OLT 200 may lose synchronization information and may transition from the normal state to the initial state. In order to prevent this situation, the Timing Unit 440 provides the IN-SERVICE Pattern formed by generating a “1010 ...” bit string for an empty time period, thereby providing a continuous mode receiver 201 of the OLT 200. It is possible to maintain a steady state without transitioning to the initial state.

T _p , T ₁ for generating the three timing patterns of FIG. , T ₂ The values of the parameters and time division bandwidth information on the ONU / ONT in service may be set and changed through a control signal input channel of the timing unit 440. That is, the control unit of the OLT 200 is T _p , T ₁ through the input channel of the Timing Unit 440. , T ₂ It is possible to set and change the values of parameters and time division bandwidth information for the ONU / ONT in service. Settings and changes can be made according to operator instructions.

For reference, since the receiver structure of the OLT according to the present invention does not affect the dynamic range performance of the receiver, it is clear that the problem due to the variation of the optical signal strength due to the different transmission path loss has to be solved by a separate method.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a configuration diagram of a conventional TDMA-PON.

2 is a TDMA-PON configuration diagram according to the present invention.

3 is a block diagram of a typical continuous mode receiver.

4 is a block diagram of a continuous mode receiver constituting the OLT of FIG. 2 in accordance with an embodiment of the present invention.

5 is an exemplary diagram of timing patterns provided by the timing unit of FIG. 4.

Claims (10)

In the optical line terminal constituting the optical subscriber network of the time division multiple access method, Continuous mode signal processing elements for recovering clock and data from the burst signal transmitted from the optical network termination device and clock data recovery circuit which is the signal processing element for the continuous mode are in a normal state. A continuous mode receiver including a timing unit providing a timing pattern to maintain a timing pattern; Optical line terminal system comprising a. The method of claim 1, And the timing unit supplies a first timing pattern to the clock data recovery circuit such that the clock data recovery circuit transitions from an initial state to a normal state when the optical line terminal is powered on. The method of claim 1, And the timing unit supplies a second timing pattern to the clock data recovery circuit so that the clock data recovery circuit maintains a normal state during a discovery process of the optical line terminal. The method of claim 3, The timing unit generates the second timing pattern in which the first bit pattern and the second bit pattern are repeated with a parameter specifying a bit string length of a first bit pattern and a parameter specifying a bit string length of a second bit pattern. New fiber termination device registration method characterized in that. The method of claim 4, wherein And the first bit pattern is a bit pattern in which 1 bit and 0 bits are repeated, and the second bit pattern is a bit pattern in which 0 bits are repeated. The method of claim 1, The timing unit is configured to perform a third timing such that the clock data recovery circuit maintains a normal state in a time interval in which the bandwidth is not allocated to the registered optical network termination devices while the optical line terminal communicates with the registered optical network termination devices. And a pattern is supplied to said clock data recovery circuit. In the receiver for receiving the optical signal of the burst mode in which the optical line terminal constituting the optical subscriber network of the time division multiple access method is transmitted from the optical network termination device, A photodetector for receiving the optical signal and converting the optical signal into an electrical signal; A transimpedance amplifier for amplifying the converted electrical signal; A limiting amplifier for amplifying the electrical signal amplified by the transimpedance amplifier; A clock data recovery circuit for recovering clock and data from the signal amplified by the limiting amplifier; And A timing unit for providing a timing pattern so that the clock data recovery circuit can maintain a normal state; Continuous mode receiver comprising a. The method of claim 7, wherein And the timing unit supplies a first timing pattern to the clock data recovery circuit so that the clock data recovery circuit transitions from an initial state to a normal state when the optical line terminal is powered on. The method of claim 7, wherein And the timing unit supplies a second timing pattern to the clock data recovery circuit so that the clock data recovery circuit maintains a normal state during a discovery process of the optical line terminal. The method of claim 7, wherein The timing unit may further include a third timing pattern such that the clock data recovery circuit maintains a normal state in a time interval in which bandwidth is not allocated to the registered optical network termination devices while the optical line terminal and the registered optical network termination devices are in communication. And supplying the clock data to the clock data recovery circuit.

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