KR20100060903A - Gigabit-capable passive optical network system - Google Patents

Abstract

PURPOSE: An ONT(Optical Network Terminal), an OLT(Optical Line Terminal) and GPON(Gigabit Passive Optical Network) comprising these are provided to apply variably generated delay time generated with the variable in bit unit by data bus size by UL/DL transmission rate and by clock frequency to distance measurement thereby exactly measuring distance of ONTs in bit unit. CONSTITUTION: A DL(DownLink) frame demultiplexer(413) extracts a distance measurement request message by inverse multiplexing of a downward frame. An UL(UpLink) transmission controller(414) controls transmission time of an UL frame by calculation of time for start bit search time of the downward frame and UL/DL clock deviation. An UL frame multiplexer](415) performs delayed output of upward frame as time of calculated byte unit. A bit unit delay unit(416) performs delay output of the upward frame as time of calculated residual bit unit.

Description

GIGABIT-CAPABLE PASSIVE OPTICAL NETWORK SYSTEM} Optical fiber termination device and optical line terminal device and gigabit passive optical network system including them

The present invention relates to a passive optical network system, and more particularly, to a gigabit passive optical network system providing an asymmetric transmission rate, and an optical network terminator and an optical network circuit device constituting the system.

This study is 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]

The Gigabit Passive Optical Network (GPON) system is one of FTTH (Fiber to the Home) technology standardized through ITU-T to provide broadband to subscribers and to accommodate various multi-protocols. A plurality of optical network terminals (hereinafter referred to as ONTs) are connected to a single optical line terminal (OLT) through a passive element. Subscriber network transmission technology connected in a way.

Since the GPON technology uses TDMA (Time Division Multiple Access) transmission upward, it accurately measures the distance from ONTs located at different locations and assigns a correction value (EqD, Equalization Delay) to service without collision between each other. Should be. That is, in GPON, all ONTs must be aligned in time so that the OLT can be reached in the same virtual time.

For reference, GPON assigns a correction value according to Round Trip Delay (RTD) to ONTs by setting a time of 250us as a reference time to guarantee a maximum physical distance of 20 km (PON link distance). When the distance measurement for the ONTs is completed, the signals are delayed by the assigned correction value and the ONTs are aligned in the same virtual time in time. For reference, the correction value EqD is calculated by Equation 1 below.

Correction value (EqD) = 250us-distance measurement time (RTD)

1 and 2 are diagrams for explaining a concept of distance measurement between the OLT 100 and the ONT 110 defined in the GPON standard.

Referring to FIG. 1, in order to measure the distance between the ONTs 110 in the GPON, the E / O conversion time Tis1 or the O / E conversion time Tio2 and the ONT device 110 in the OLT device 100 are measured. O / E conversion time (Tio1) or E / O conversion time (Tis2), propagation delay time (2 * Tpd) of GPON link 108, response processing delay time (Ts) in ONT device 110, etc. This is used. Therefore, the distance measurement time (RTD) with the ONT device may be defined as in Equation 2 below.

Distance measurement time (RTD) = (2 * Tpd) + (Tis1 + Tio1 + Tis2 + Tio2) + (Ts)

Referring to Figure 2 in more detail how to measure the distance between the ONT in GPON,

First, in GPON, the OLT 200 transmits a GPON TC layer specifications (GTC) frame to the ONTs 201 and 202 at 125us cycles. The GTC frame transmitted downward has a synchronization field value of 4 bytes, and the ONTs 201 and 202 find this value and maintain a 125us period synchronized with the OLT 200. In GPON, the distance measurement is performed separately after the ONT values are assigned to the ONTs 201 and 202. These ONTs 201 and 202 must be in a distance measurement mode for distance measurement.

As shown in FIG. 2, when the OLT 200 sends a request message 203 for ranging to the ONT1 201, the OLT 200 sends the distance until the response 205 for this request comes. The measurement time RTD is calculated 206. Upon receiving the ranging request message 203, the ONT1 201 waits for the minimum ONU response time and transmits the ranging response message to the OLT 200 at the Sstart value time 204 displayed in the ranging request message. When the OLT 200 receives the normal ranging response message, the calculation of the ranging time 206 for ONT1 is completed.

GPON, on the other hand, uses the clock frequency of uplink speed for distance measurement of ONT. As shown in FIG. 2, the ONT1 201 located at the 10 km position takes a transfer delay time of 100us round trip in the optical link. When the ONT2 202 receives the distance measurement request message similarly to the ONT1 201, the ONT2 202 transmits the distance measurement response message to the OLT 200 according to a predetermined rule to complete the distance measurement.

In order to accurately measure the distance of the ONTs, the calculation is easy when the up / down clock frequencies of the OLT and the ONT are the same. For reference, in case of GPON supporting downlink 2.488Gbps and uplink 1.244Gbps, 155.52MHz is used as up / down transmission clock frequency.

However, the same standard cannot be used for the up / down transmission clock frequencies for the next standard GPON, which provides downlink 9.952Gbps and uplink 1.244Gbps or 2.488Gbps. The reason is that GPON must use a 64-bit data bus and a clock frequency of 155.52 MHz to provide a transmission rate of 9.952 Gbps downward, while 16-bit data can be used to provide a transmission rate of 1.244 Gbps and a 2.488 Gbps upward. This is because the bus and a clock frequency of 77.76MHz or 155.52MHz must be used.

Therefore, in order to measure the exact bitwise distance of ONTs in asymmetric GPONs with different up / down clock frequencies, the PON MAC measures the distance by considering the delay for the bitwise processing and the delay time that varies with the up / down clock frequency. The time (RTD) must be calculated.

Accordingly, the present invention finds delay times that are variable according to data bus size and clock frequency according to up / down transmission speeds in a gigabit passive optical network providing an asymmetric transmission rate, and reflects them in the distance measurement time. To provide an optical network terminal device and an optical line terminal device that can accurately measure the distance of the devices in units of bits,

Furthermore, the present invention provides a gigabit passive optical network system including the optical network termination device and the optical line terminal device.

It is still another object of the present invention to provide a passive optical network system, an optical line terminal device, and an optical network termination device capable of accurately measuring the distance of optical network termination devices in units of bits in a passive optical network system providing an asymmetric transmission rate. .

Passive optical network (PON) system providing an asymmetric transmission rate according to an embodiment of the present invention for achieving the above object,

The distance of the fiber termination device is measured by calculating the time from the time when the downlink frame containing the distance measurement request message is transmitted until the response message is received, but reflects the starting position search time of the uplink frame in bits. Optical line terminal device for measuring the distance of;

One or more optical network terminators for calculating the time generated by the start bit search time of the downlink frame and the up / down clock deviation from the start bit search position of the downlink frame and delaying the transmission time of the uplink frame up to a bit unit; It is characterized by.

In addition, the optical line terminal device of the GPON system providing an asymmetric transmission rate according to an embodiment of the present invention,

A downlink frame multiplexer configured to receive a distance measurement request message and generate a downlink frame;

An uplink frame search unit for searching for a start position of an uplink frame transmitted in response to the transmission of the distance measurement request message;

An uplink frame demultiplexer for demultiplexing the uplink frame to extract a distance measurement response message;

The distance of the fiber termination device is measured by calculating the time from the time when the downlink frame including the distance measurement request message is transmitted to the time when the response message is received, and the distance measurement is performed by reflecting the start position search time of the uplink frame in bits. It comprises a; distance measuring unit for.

Furthermore, the optical network termination device of the GPON system providing an asymmetric transmission rate according to an embodiment of the present invention,

A down frame search unit for searching for a start bit of a down frame;

A downlink frame demultiplexer for demultiplexing the downlink frame to extract a distance measurement request message;

An uplink transmission control unit for controlling a transmission time of an uplink frame by calculating a time generated due to a start bit search time of the downlink frame and an up / down clock deviation from the searched start bit search position of the downlink frame;

An upward frame multiplexer for generating an uplink frame by receiving a distance measurement response message and delaying outputting the uplink frame by the time in bytes calculated by the uplink control unit;

And a bit unit delay unit for delaying and outputting an uplink frame transmitted by the uplink multiplexer by the time of the remaining bit unit calculated by the uplink control unit.

According to the problem solving means as described above, the present invention in the GPON system that provides an asymmetric transmission rate, the distance measurement to find the delay time that is variablely generated according to the data bus size and the clock frequency according to the up / down transmission rate By reflecting on, the distance of the optical network terminators (ONT) can be accurately measured in units of bits.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In the following description, an embodiment of the present invention will be described assuming a gigabit passive optical network system as a passive optical network.

First, FIG. 3 illustrates a block diagram of a GPON system providing an asymmetric transmission rate according to an embodiment of the present invention. More specifically, FIG. 3 provides a transmission rate of 9.952 Gbps and 1.244 Gbps or 2.488 Gbps. A schematic diagram of a GPON system is shown.

As shown, the GPON system according to the embodiment of the present invention calculates the time from the transmission of the downlink GTC (GPON TC layer specifications) frame containing the distance measurement request message until the response message is received ONT (400) While measuring the distance of the OLT (300) for measuring the distance of the ONT (400) by reflecting the start position search time of the uplink GTC frame, and the start of the downlink GTC frame from the start bit search position of the downlink GTC frame Comprising one or more ONT (400) to delay the transmission time of the uplink GTC frame to the bit unit by calculating the time generated by the bit search time and the up / down clock deviation. For reference, the distance measurement in the GPON system is performed in the GTC layer and transmitted through the GTC frame.

In the above-described GPON system, the PON MAC 310 of the OLT 300 and the PON MAC 410 of the ONT 400 each have a 64-bit data bus and a clock of 155.52 MHz to provide a transmission rate of 9.952 Gbps downward. It uses a frequency and uses a 16-bit data bus and a clock frequency of 77.76 MHz to provide an uplink transmission rate of 1.244 Gbps. It uses a 16-bit data bus and a clock frequency of 155.52MHz to provide an uplink 2.488Gbps transfer rate.

3, the PON MAC 310 of the OLT 300 includes a downlink GTC frame multiplexer 311, a SERDES 312, and a distance measurer 313 for distance measurement of the ONT 400. The uplink GTC frame search unit 314 and the uplink GTC frame demultiplexer 315 are included.

The downlink GTC frame multiplexer 311 continues to transmit the GTC frame at 125us periods, receives the distance measurement request message, and multiplexes the downlink to the downlink GT frame frame. The SERDES 312 converts the downlink GTC frame of the 64-bit bus into 16-bit bus data using a clock frequency four times faster according to the interface of the external MUX chip 320.

The uplink GTC frame search unit 314 uses a bit-wise searching method on a 16-bit data bus input from an external DEMUX chip 350 to determine a start position of an uplink frame, that is, a 16-bit delimiter. Locate and extract the uplink GTC frame.

The uplink GTC frame demultiplexer 315 extracts the distance measurement response message included in the uplink GTC frame, and the distance measurer 313 starts the time from when the downlink GTC frame containing the distance measurement request message is transmitted. The distance of the ONT 400 is measured by calculating the time until the response message is received, and the distance is measured by reflecting the start position search time of the uplink GTC frame in bits. In this case, the time measurement uses the up clock frequency.

Meanwhile, the PON MAC 410 of the ONT 400 according to an embodiment of the present invention includes a SERDES 411, a downlink GTC frame search unit 412, and a downlink GTC frame demultiplexer 413 in response to a distance measurement request. And an uplink transmission control unit 414, an uplink GTC frame multiplexer 415, and a bit unit delay unit 416.

The SERDES 411 converts 16-bit data input from the external DEMUX chip 430 into 64-bit data, and the downlink GTC frame search unit 412 uses a 32-bit search method on 64-bit input data. The downlink frame start bit, that is, the Psync field is found to maintain the same synchronization as the OLT 300 of the downlink GTC frame. And transmits the start bit position value found the Psync to the uplink transmission controller 414 to be described later.

The downlink GTC frame demultiplexer 413 extracts the distance measurement request message included in the downlink GTC frame and transmits it to the uplink transmission controller 414 together with the synchronization signal.

The uplink transmission controller 414 controls the transmission time of the uplink GTC frame by calculating a time generated by the start bit search time of the downlink GTC frame and the up / down clock deviation from the searched start bit search position of the downlink GTC frame. It also performs a distance response message request.

The uplink GTC frame multiplexer 415 receives the distance measurement response message in the ranging mode to generate an uplink GTC frame, and generates the uplink GTC frame by the time in bytes calculated by the uplink transmission controller 414. Delay output. The uplink GTC frame multiplexer 415 provides a function of transmitting an uplink GTC frame by the time allocated by the OLT 300 in an operation mode.

The bit delay unit 416 delays and outputs an uplink GTC frame transmitted by the uplink GTC frame multiplexer 415 by the remaining bit units within 8 bits calculated by the uplink control unit 414.

Hereinafter, the distance measuring procedure in the GPON system having the above-described configuration will be described in detail with reference to the accompanying drawings. 4 is a diagram illustrating a downlink GTC frame configuration, and FIG. 5 is a diagram for explaining a search for a start bit position of a downlink GTC frame. FIG. 6 is a diagram for explaining bit deviations according to different clock frequencies, and FIG. 7 is a block diagram of an uplink GTC frame.

First, FIG. 4 shows a structure diagram of a downlink GTC frame a. As shown in Fig. 4, the distance measurement request message b is constructed using 8 bytes of band allocation information. In the AllocID field of the distance measurement request message (b), an identifier value of the ONT that performs the distance measurement is recorded, and a transmission band is allocated 13 bytes. Also, to request the ranging response, set the 11th bit of the Flag field to '1'. The distance measurement request message (b) is inserted into the uplink allocation field (US BW MAP) of the downlink GTC frame 403 and transmitted.

Meanwhile, the downlink GTC frame multiplexer 311 generates and transmits a downlink GTC frame including the distance measurement request message (b) as shown in FIG. 4. The distance measuring unit 313 starts the distance measurement with the ONT (400). Because distance measurement uses an upward clock frequency, time is measured using a counter that counts from 0 to 9719. The downlink GTC frame is transmitted to the PON link through the SERDES 312 through the photoelectric (E / O) conversion with the external MUX chip 320. For reference, blocks that are responsible for downlink GTC frame transmission in the PON MAC 310 of the OLT 300 have a fixed processing time.

Meanwhile, the downlink GTC frame transmitted through the PON link is input to the SERDES 411 of the ONT 400 and the PON MAC 410 through the photoelectric conversion (O / E) 420 block and the DEMUX chip 430. Is processed and output. These blocks also signal with a fixed processing time.

The downlink GTC frame search unit 412 finds the start position (Psync field) of the downlink GTC frame input in 125us periods through bit unit comparison. As shown in FIG. 5, since the input data is 64 bits 500, a variable time 501 of up to 63 bits is delayed according to the position 502 of finding Psync.

The PON MAC 410 of the ONT 400 applies a synchronization signal of 125us period synchronized with the OLT 300 after finding Psync. Therefore, the 63-bit variable time 501 used to find the Psync is not included in the GTC frame synchronization period of the ONT 400 and should be reflected in the distance measurement.

The downlink GTC frame demultiplexer 413 extracts the distance measurement request message included in the downlink GTC frame and transmits the same with the synchronization signal output from the point of time when Psync is found. The GTC frame demultiplexer 413 also has a fixed processing time.

The uplink transmission controller 414 calculates a delay amount (or delay time) in units of bits using the downlink frame start bit position information found by the downlink GTC frame search unit 412. Since the distance measurement in the OLT 300 uses an upward clock frequency, the time of 8 bits downward is calculated as the time of 1 bit upward as shown in Equation 3 below. That is, the uplink transmission controller 414 delays the bits of the uplink GTC frame by an integer value obtained by dividing the Psync start bit position by eight. The uplink transmission control unit 414 calculates the start bit search time of the downlink frame by multiplying an integer value obtained by dividing the start bit search position bit of the downlink frame by the time ratio of the uplink and downlink bits, and calculating the start bit search time of the downlink frame. It will mean the same as delaying the transmission of a frame. For reference, in the operation mode other than the ranging mode, 8 bits or less of the allocated correction value is added.

Bit delay = (Psync start bit position / 8) + EqD bit value

In addition, the uplink transmission controller 414 uses 155.52 MHz as the down clock frequency and 77.76 MHz as the up clock frequency to generate 8-bit deviations, as shown in FIG. 6. As shown in FIG. 6, the up / down clock frequencies are different. The synchronization signal input to the GTC frame demultiplexer 413 may be generated at the rising edge of the first clock pulse of 77.7 MHz or may be generated at the first falling edge. Therefore, the 8-bit delay when the synchronization signal occurs on the falling edge must be further reflected in the distance measurement. If the ONT 400 provides an uplink 2.488 Gbps transmission rate, since 155.52 MHz is used as an up clock frequency, an 8-bit deviation will not occur.

In addition, the uplink transmission controller 414 must control the GTC frame synchronization signal 602 synchronized to 77.7MHz to transmit an uplink GTC frame at the start time of the request message after a delay of 35us response delay time 604. Accordingly, the uplink transmission control unit 414 controls all transmission time of the uplink frame by the number of bits corresponding to the above time by integrating all the time, but the byte unit is controlled by the uplink GTC frame multiplexer 415, 8 bits The following bit units are controlled by the bit unit delay unit 416.

On the other hand, the uplink GTC frame multiplexer 415 receives the distance measurement response message (b) as shown in FIG. 7 and delays the uplink GTC frame 701 by the time in bytes calculated by the uplink transmission controller 414. send. For reference, the distance measurement response message (b) is inserted into the PLOAM message section of 13 bytes. The ranging response message includes its own ONUID value assigned by the OLT 300 and a message ID value indicating the response message, and its own vendor ID information and serial number information. In order to transmit the ranging response message, the state of the ONT 400 must be in a ranging mode.

The bit delay unit 416 receives the bit delay information within 8 bits from the uplink transmission controller 414 and delays the uplink GTC frame. That is, the bitwise delay unit 416 provides a bitwise delay in the GPON. The uplink GTC frame delayed by the bit delay unit 416 is then transmitted through the PON link through the MUX chip 440 of the ONT 400 and the photoelectric (E / O) conversion 450.

The uplink GTC frame received by the OLT 300 through the PON link is input to the PON MAC 310 as 16-bit data through the photoelectric (O / E) conversion 340 of the OLT 300 and the DEMUX chip 350. . The uplink GTC frame search unit 314 then finds a 16-bit delimiter that is a frame start position through bit-wise comparison on the 16-bit data. The uplink GTC frame search unit 314 generates a variable deviation of up to 15 bits depending on the start position of the delimiter value as in the downlink. This deviation information is reflected in the distance measurement by the distance measuring unit 313.

When the GTC frame demultiplexer 315 extracts the distance measurement response message from the uplink GTC frame and transmits the distance measurement response message to the distance measurement unit 313, the distance measurement unit 313 compares the information of the distance measurement response message to be a normal response message. If so, the calculation of the distance measurement time ends. The distance measurement time calculation formula is shown in Equation 4 below.

Distance measurement time (RTD) = PON link propagation delay time (2 * Tpd)

+ Photoelectric conversion time (Tis1 + Tio1 + Tis2 + Tio2)

+ ONT PON MAC processing time (Ts)

+ Down GTC frame start bit position time

+ Time caused by up / down clock deviation

+ Up GTC frame start bit position time

That is, the distance measuring unit 313 of the OLT 300 calculates the time from the time when the downlink frame containing the distance measurement request message is transmitted to the time when the response message is received, and measures the distance of the optical network terminator, but the uplink frame Reflects the start position search time in bit units.

Therefore, the present invention is able to accurately measure the distance of the ONT (400) in the GPON to provide an asymmetric transmission rate up to the bit unit.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Accordingly, the true scope of the present invention should be determined only by the appended claims.

1 and 2 are diagrams for explaining a concept of distance measurement between the OLT 100 and the ONT 110 defined in the GPON standard.

Figure 3 is a block diagram of a GPON system providing an asymmetric transmission rate in accordance with an embodiment of the present invention.

4 is a downlink GTC frame configuration diagram.

5 is a diagram for explaining a search for a start bit position of a downlink GTC frame.

FIG. 6 is a diagram for explaining bit deviations according to different clock frequencies.

7 is an uplink GTC frame configuration diagram.

Claims (12)

In the optical fiber terminator of a passive optical network system providing an asymmetric transmission rate, A down frame search unit for searching for a start bit of a down frame; A downlink frame demultiplexer for demultiplexing the downlink frame to extract a distance measurement request message; An uplink transmission control unit for controlling a transmission time of an uplink frame by calculating a time generated due to a start bit search time of the downlink frame and an up / down clock deviation from the searched start bit search position of the downlink frame; An uplink multiplexer configured to generate an uplink frame by receiving a distance measurement response message and delay output the uplink frame by a time in bytes calculated by the uplink control unit; And a bit unit delay unit for delaying and outputting the uplink frame transmitted by the uplink multiplexer by the time remaining in the unit of the bit calculated by the uplink transmission control unit. The method of claim 1, wherein the uplink transmission control unit, And a start bit search time of the downlink frame is calculated by multiplying an integer value obtained by dividing the start bit search position bit of the downlink frame by a time ratio of the uplink and downlink bits. The method of claim 1, wherein the uplink transmission control unit, An optical network terminator characterized by setting the 8-bit deviation generated by the use of the down clock frequency 155.52 MHz and the up clock frequency 77.76 MHz to the time caused by the up / down clock deviation. In the optical line terminal device of a passive optical network system providing an asymmetric transmission rate, A downlink frame multiplexer configured to receive a distance measurement request message and generate a downlink frame; An uplink frame search unit for searching for a start position of an uplink frame transmitted in response to the transmission of the distance measurement request message; An uplink frame demultiplexer for demultiplexing the uplink frame to extract a distance measurement response message; The distance of the fiber termination device is measured by calculating the time from the time when the downlink frame including the distance measurement request message is transmitted to the time when the response message is received, and the distance measurement is performed by reflecting the start position search time of the uplink frame in bits. Optical line terminal device of a passive optical network system comprising a; distance measuring unit for. The method of claim 4, wherein the distance measurement time calculated by the distance measuring unit includes: a passive optical network (PON) link propagation delay time, a photoelectric conversion time, a PON MAC processing time in an optical network end device, a downlink start bit search time, and phase / An optical line terminal apparatus comprising a time generated due to a downward clock deviation and an uplink start bit search time. In a passive optical network (PON) system that provides an asymmetric transmission rate, The distance of the fiber termination device is measured by calculating the time from the time when the downlink frame containing the distance measurement request message is transmitted until the response message is received, but reflects the starting position search time of the uplink frame in bits. Optical line terminal device for measuring the distance of; One or more optical network terminators for calculating the time generated by the start bit search time of the downlink frame and the up / down clock deviation from the start bit search position of the downlink frame and delaying the transmission time of the uplink frame up to a bit unit; Passive optical network system characterized in that. The method according to claim 6, The optical line terminal device, A downlink frame multiplexer configured to receive a distance measurement request message and generate a downlink frame; An uplink frame search unit for searching for a start position of an uplink frame transmitted in response to the transmission of the distance measurement request message; An uplink frame demultiplexer for demultiplexing the uplink frame to extract a distance measurement response message; The distance of the fiber termination device is measured by calculating the time from the time when the downlink frame including the distance measurement request message is transmitted to the time when the response message is received, and the distance measurement is performed by reflecting the start position search time of the uplink frame in bits. Passive optical network system comprising a; distance measuring unit for. The apparatus of claim 7, wherein the distance measurement time calculated by the distance measuring unit includes: a passive optical network (PON) link propagation delay time, a photoelectric conversion time, a PON MAC processing time in an optical network termination device, a downlink start bit search time, and phase / Passive optical network system characterized by including the time caused by the down clock deviation and the uplink start bit search time. The method according to claim 6 or 7, wherein the optical network termination device, A down frame search unit for searching for a start bit of a down frame; A downlink frame demultiplexer for demultiplexing the downlink frame to extract a distance measurement request message; An uplink transmission control unit for controlling a transmission time of an uplink frame by calculating a time generated by a start bit search time of a downlink frame and an up / down clock deviation from a searched start bit search position of the downlink frame; An uplink multiplexer configured to generate an uplink frame by receiving a distance measurement response message and delay output the uplink frame by a time in bytes calculated by the uplink control unit; And a bit unit delay unit for delaying and outputting an uplink frame transmitted by the uplink multiplexer by the time remaining in the unit of the bit calculated by the uplink control unit. The method of claim 9, wherein the uplink transmission control unit, Passive optical network system, characterized in that to calculate the start bit search time of the downlink frame by multiplying the integer time of the start bit search position bit of the downlink by the time ratio of the up and down bits. 10. The passive optical network system of claim 9, wherein the optical fiber terminator has a transmission rate of uplink 1.244Gbps or uplink 2.488Gbps. 9. The passive optical network system according to any one of claims 6, 7, and 8, wherein the optical line terminal apparatus has a transmission rate of 9.952 Gbps downward.

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