CN111901706B

CN111901706B - ONU discovery ranging method and system in TDM PON

Info

Publication number: CN111901706B
Application number: CN202010551946.2A
Authority: CN
Inventors: 刘新峰; 王志军; 常宇光
Original assignee: China Information And Communication Technology Group Co ltd; Fiberhome Telecommunication Technologies Co Ltd
Current assignee: China Information And Communication Technology Group Co ltd; Fiberhome Telecommunication Technologies Co Ltd
Priority date: 2020-06-17
Filing date: 2020-06-17
Publication date: 2022-05-06
Anticipated expiration: 2040-06-17
Also published as: CN111901706A

Abstract

The invention discloses an ONU discovery and ranging method in a TDM PON, which comprises the following steps: OLT broadcasts discovery request message to ONU which is on-line and added newly; after receiving the discovery request message, the newly added ONU sends a discovery response message to the OLT through a set-top mechanism; after receiving the discovery response message, the OLT determines a corresponding newly-added ONU according to the discovery response message and sends a ranging request message to the newly-added ONU; after receiving the ranging request message, the newly added ONU replies a ranging response message through a set-top mechanism; and after receiving the ranging response message, the OLT calculates the distance between the newly added ONU and the OLT. The method of the invention adopts the baseband remodulation optical modulation technology, adopts the optical power superposition technology and the like, and solves the function of multipoint-to-point transmission. The invention also provides a corresponding ONU discovery ranging system in the TDM PON.

Description

ONU discovery ranging method and system in TDM PON

Technical Field

The invention belongs to the technical field of optical communication, and particularly relates to an ONU (optical network unit) discovery and ranging method and an ONU discovery and ranging system in a TDM PON (time division multiplexing passive optical network).

Background

A Passive Optical Network (PON) technology is a point-to-multipoint Optical fiber access technology, and is composed of an Optical Line Terminal (OLT) on a central office side, an Optical Network Unit (ONU) on a subscriber side, and an Optical Distribution Network (ODN). The downlink data flow of the traditional TDM (Time-Division Multiplexing) PON system adopts a broadcasting technology, and the uplink data flow adopts a TDM technology, so as to solve the Multiplexing problem of signals in each direction of multiple users.

In the existing TDM PON, because different ONU and OLT have different distances, time delay compensation is needed to avoid sending collision; the distance measurement is needed when the time delay compensation is carried out; meanwhile, the newly added ONU needs to perform OLT discovery. In order to avoid the collision of the ONU newly joining the network with the normal upstream burst during the sequence number acquisition phase and the ranging phase, the conventional TDM PON ranging scheme must suspend the upstream transmission of the ONU in operation during the time period when the upstream burst from the new ONU is expected to be received, which is called the silence window. The silence window typically causes delays and jitter in the transmissions of the on-line ONU of more than 250 mus.

It is estimated that 5G indoor application accounts for more than 85%, and 5G is worse in wall penetration in the use frequency band, so that the demand for 5G digital indoor distribution bearing is more and more. The characteristics of the PON system networking structure, the covered geographical position, flexibility, quick implementation and the like are more suitable for 5G digital indoor distribution bearing, so that the research on the PON bearing 5G indoor distribution is of great significance. However, since the 5G bearer is sensitive to delay, jitter and the like, and the conventional TDM PON is designed for home networking, the related technical indexes cannot meet the application requirements, and therefore, the TDM PON urgently needs a new technology to improve the technical indexes. In order to solve the delay jitter of the TDM PON, it is proposed to solve this problem with a single wavelength, but the number of optical transceivers increases due to the newly added wavelength, and the cost, power consumption, and the like of the system increase more.

Disclosure of Invention

Aiming at the defects or the improvement requirements in the prior art, the invention provides the ONU discovery ranging method and the ONU discovery ranging system in the TDM PON.

To achieve the above object, according to an aspect of the present invention, there is provided an ONU discovery ranging method in a TDM PON, the method including:

OLT broadcasts discovery request message to ONU which is on-line and added newly;

after receiving the discovery request message, the newly added ONU sends a discovery response message to the OLT through a set-top mechanism;

after receiving the discovery response message, the OLT determines a corresponding newly-added ONU according to the discovery response message and sends a ranging request message to the newly-added ONU;

after receiving the ranging request message, the newly added ONU replies a ranging response message through a set top mechanism, wherein the ranging response message comprises processing delay information of the newly added ONU;

and after receiving the ranging response message, the OLT calculates the distance between the newly added ONU and the OLT according to the sending time of the ranging request message, the receiving time of the ranging response message and the processing delay information of the newly added ONU.

In an embodiment of the present invention, the broadcasting, by the OLT, of the discovery request message to the on-line and newly-added ONUs specifically includes:

adopting a frame structure OAM in a high-speed data frame of the TDM PON to carry the discovery request message; or sending the discovery request message through a set-top mechanism.

In an embodiment of the present invention, after receiving the discovery response message, the OLT determines a corresponding newly added ONU according to the discovery response message, and specifically includes:

and the OLT determines the newly added ONU by comparing the optical power of the superposed tuning signal with the previously recorded optical power change without the superposed tuning signal and performing decoding and message interaction, and determines the ONU ID of the newly added ONU through message interaction.

In an embodiment of the present invention, the OLT discovery request message is sent by performing a set-top modulation on the basis of the high-speed sending data of the OLT; and the optical power of the tuning signal of the discovery response message and the ranging response message of the newly added ONU is superposed on the optical power of the ONU which is carrying out high-speed data transmission on line.

In an embodiment of the present invention, the discovery request message sent by the OLT includes an initial optical power of a set-top signal, where the initial optical power of the set-top signal specifically is: and calculating the maximum optical power allowed by the tuning signal by monitoring the receiving optical power of each on-line ONU on the OLT, and informing the ONU as the initial optical power.

In one embodiment of the invention, the method further comprises: and adjusting the optical power of the newly added ONU by using the optical power level adjusting function of the PON through the ONU notified by the top-adjusting signal of the high-speed data frame or the frame structure OAM of the OLT.

In one embodiment of the invention, the method further comprises: after ranging is completed, a lead code with relatively large uplink physical layer overhead is set, and the number of lead code bytes is gradually reduced by matching with the phase monitoring and balanced delay updating functions of the OLT.

According to another aspect of the present invention, there is also provided an ONU discovery ranging system in a TDM PON, including an OLT device and an ONU device, where the ONU device includes a set-top transmission subunit, and the OLT device includes a set-top reception subunit, where:

the OLT is used for broadcasting a discovery request message to the on-line ONU and the newly added ONU;

the top-tuning sending subunit of the newly added ONU is configured to send a discovery response message to the OLT through a top-tuning mechanism after the newly added ONU receives the discovery request message;

the top-tuning receiving subunit of the OLT is configured to receive the discovery response message, and the OLT is configured to determine a corresponding newly added ONU according to the discovery response message and send a ranging request message to the newly added ONU;

the top-tuning sending subunit of the newly added ONU is configured to reply a ranging response message through a top-tuning mechanism after the newly added ONU receives the ranging request message, where the ranging response message includes processing delay information of the newly added ONU;

and the top-tuning receiving subunit of the OLT is used for receiving the ranging response message, and the OLT is used for calculating the distance between the newly-added ONU and the OLT according to the sending time of the ranging request message, the receiving time of the ranging response message and the processing delay information of the newly-added ONU.

In an embodiment of the present invention, the ONU further includes a set-top reception subunit, and the OLT further includes a set-top transmission subunit, where:

the top-tuning sending subunit of the OLT is used for broadcasting a discovery request message to the on-line ONU and the newly-added ONU;

and the tune-up receiving subunit of the ONU is used for receiving the discovery request message.

In an embodiment of the present invention, the discovery request message sent by the OLT is sent by performing a set-top modulation based on the high-speed sending data of the OLT; and the optical power of the tuning signal of the discovery response message and the ranging response message of the newly added ONU is superposed on the optical power of the ONU which is carrying out high-speed data transmission on line.

Generally, compared with the prior art, the technical scheme of the invention has the following beneficial effects:

the invention uses the baseband remodulation optical pilot tone as a ranging and management channel, does not need to open a silent window in the process of receiving and transmitting high-speed data, and can perform ranging synchronously with the data, thereby reducing jitter and time delay. And a separate optical transceiver and a separate wavelength do not need to be newly added to make a ranging and management channel, so that the system has great advantages in the aspects of use cost, power consumption and the like.

Drawings

Fig. 1 is a schematic diagram of a networking of an OLT and an ONU in an embodiment of the present invention;

fig. 2 is a schematic flowchart of an ONU discovery ranging method in a TDM PON according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a principle of superposition of optical power of a pilot tone in an embodiment of the present invention;

fig. 4 is a schematic flowchart of an ONU discovery ranging method in a TDM PON according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of an ONU discovery ranging system in a TDM PON according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of another ONU discovery ranging system in a TDM PON according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the WDM-PON, an Auxiliary Management and Control Channel (AMCC) is required to transmit wavelength assignment, allocation information, and OAM data. The AMCC uses the same wavelength as the payload, as opposed to a separate wavelength alone. The baseband remodulation and tuning transmission usually includes two modulation modes of amplitude modulation and carrier frequency amplitude modulation, the transmission mode can be tuning transmission by a high-speed and low-speed separation mode such as LD of EML and SOA with SOA, and high and low frequencies can be isolated by a bias circuit of DML.

In a WDM PON (wavelength division passive optical network), each ONU uses one wavelength, and the ONUs and the OLT have an exclusive relationship of wavelength point to point, and since no collision occurs, it is not necessary to perform ranging. The baseband remodulation optical modulation technology is a technology for realizing an AMCC (Auxiliary Management Control Channel) in a WDM (Wavelength Division Multiplexing) PON, and the realization thereof is also a point-to-point technology based on Wavelength and does not realize a multipoint-to-point function. The traditional TDM PON is a management channel implemented by OAM (Operations, Administration, and Maintenance) with a high-speed data frame structure, that is, a part of data in the high-speed data frame is used to carry management data messages.

The invention uses the baseband remodulation optical top modulation technology in the TDM PON, adopts the technologies of optical power superposition and the like, solves the function of multipoint-to-point transmission, does not need to start a silent window to stop high-speed data transmission when transmitting the top modulation control data to carry out ranging operation, realizes the synchronous ranging and data transmission, and does not need to increase extra optical transceiving components to occupy wavelength resources. Has the characteristics of low power consumption, low cost and the like. The method has important significance for realizing the service with low delay jitter by using the TDM PON.

Example 1

Specifically, as shown in fig. 1, in the existing TDM PON system, the ONU optical transmitting unit adds a set-top transmitting subunit, and the OLT optical receiving unit adds a set-top receiving subunit; the OLT optical sending unit can be optionally added with a set-top sending subunit, and the ONU optical receiving unit can be optionally added with a set-top receiving subunit.

In the TDM PON technology, high-speed data of an ONU is TDM-transmitted under the DBA (DBA Dynamic Bandwidth allocation) management of an OLT, and transmission time slots of different ONUs are known to the OLT. Based on the above, although the transmission optical power of the optical transmission unit of each ONU and the distance from each ONU to the OLT are different, the optical reception unit of the OLT can detect the reception optical power from each ONU to the OLT by the optical power of each different time slot and record the OLT reception optical power of each ONU.

The high-speed data of the ONU can be continuously transmitted by TDM burst data under the DBA management of the OLT, and the invention closes the function of opening the silent window in the high-speed data transmission process, thereby avoiding the delay and jitter of more than 250 mus generated by windowing transmission of the on-line ONU.

Example 2

When a newly added ONU discovery and ranging process needs to be started, the OLT broadcasts a discovery request message to each online ONU and each newly added ONU, the newly added ONU replies a discovery response message through a set-top mechanism after receiving the discovery request message and enters the discovery reply process, the OLT sends a ranging request message to the newly added ONU again after receiving the discovery response message, and the newly added ONU replies a ranging response message through the set-top mechanism and enters the ranging process after receiving the ranging request message.

As shown in fig. 2, the present invention provides an ONU discovery ranging method in a TDM PON, including:

s1, OLT broadcasts the discovery request message to the ONU which is on-line and newly joined;

discovery request message: can be related messages such as Upstream _ overflow, SN request and the like in G.984.

Generally, a frame structure OAM in a high-speed data frame of the TDM PON may be employed to carry the discovery request message; or sending the discovery request message through a set-top mechanism;

the discovery request message sent by the OLT is sent by adjusting the top modulation on the basis of the high-speed sending data of the OLT; the optical power of the tuning signal of the discovery response message and the ranging response message of the newly added ONU is superposed on the optical power of the ONU which is carrying out high-speed data transmission on line;

the discovery request message sent by the OLT includes an initial optical power of a set-top signal, where the initial optical power of the set-top signal is specifically: and calculating the maximum optical power allowed by the tuning signal by monitoring the receiving optical power of each on-line ONU on the OLT, and informing the ONU as the initial optical power.

Specifically, the initial optical power of the pilot tone signal is specifically: the maximum optical power allowed by the tuning signal is calculated according to the preset proportion (for example, 2% -8%) of the receiving optical power of each ONU on the OLT in the test empirical formula by monitoring the receiving optical power of each ONU on the OLT, and the maximum optical power is used as an initial parameter to inform the ONU.

S2, after receiving the discovery request message, the newly added ONU sends a discovery response message to the OLT through a set-top mechanism;

the discovery response message may be related messages such as Serial _ number _ ONU in g.984.

S3, after receiving the discovery response message, the OLT determines a corresponding newly added ONU according to the discovery response message and sends a ranging request message to the newly added ONU;

the OLT determines that a newly added ONU exists by comparing the optical power of the superposed pilot tone signal with the previously recorded optical power change when the pilot tone signal is not superposed and performing decoding and message interaction, and determines the ONU ID of the newly added ONU through message interaction;

specifically, the OLT determines that there is a newly added ONU by comparing the optical power of the superimposed signal with the previously recorded optical power change when there is no superimposed signal, and the code of the discovery response Message may be coded according to the known PLOAM Message format of g.984.3 and other related PON standards, for example, the PLOAM Message defined in the g.984.3 standard includes ONU ID, Message Data, CRC, etc., the ONU ID is used to identify a specific ONU, and each ONU obtains a number, that is, ONU ID, in the ranging process; the Message ID is used for identifying the Message type; the Message Data is used for bearing the payload of the Message; the CRC is a frame check sequence. And acquiring the ONU ID of the newly added ONU by decoding the message to determine the newly added ONU.

S4, after receiving the ranging request message, the newly added ONU replies a ranging response message through a set top mechanism, wherein the ranging response message contains the processing delay information of the newly added ONU;

the processing delay information of the ONU refers to the software and hardware response time between the time when the ONU receives the ranging request message and the time when the ONU sends the ranging response message;

and S5, after receiving the ranging response message, the OLT calculates the distance between the newly added ONU and the OLT according to the sending time of the ranging request message, the receiving time of the ranging response message and the processing delay information of the newly added ONU.

The specific calculation method for calculating the distance between the newly added ONU and the OLT according to the sending time of the ranging request message, the receiving time of the ranging response message, and the processing delay information of the newly added ONU is defined in the relevant standards (for example, ITU g.984 series standards and access network technical requirements), and is not described herein again.

Because the downlink high-speed data of the OLT is in a broadcasting mode, windowing action is not needed, and extra time delay and jitter are not brought. Therefore, there are two ways to implement the downlink message, one is to use the frame structure OAM in the high-speed data frame of the original traditional TDM PON to carry, the other is to add a set-top transmission subunit in the OLT optical transmission unit to transmit through a set-top mechanism, and add a set-top reception subunit in the ONU to receive through the set-top mechanism. Either the downlink discovery request message or the ranging request message may be transmitted in the above manner. The OAM of the frame structure bears the downlink message, so that an optical sending and top-adjusting unit of the OLT and a top-adjusting receiving unit of the ONU can be saved, and the cost is lower.

In the embodiment of the present invention, encoding and decoding may be performed according to formats of uplink and downlink messages defined in the g.984.3 standard, such as Serial _ number _ ONU, Upstream _ Overhead, Assign _ ONU ID, and Ranging _ Time.

As shown in fig. 3, when a newly added ONU transmits a tune-to-top message, in the TDM PON, since the upstream wavelengths of the ONUs are the same, the optical power waveform of the low-speed tune-to-top management data is superimposed with the optical power waveform of one or more high-speed traffic data being transmitted at the receiving end of the OLT. In order to reduce the interference error code generated by the low-speed ceiling regulating management data on the normal receiving and sending of the high-speed service data as much as possible, the optical power of the low-speed ceiling regulating management data used in the invention is far lower than that of the high-speed service data. Because the optical power of each ONU when no pilot signal is superposed is recorded before the OLT, the pilot receiving subunit of the OLT can obtain the pilot message sent by the newly added ONU by comparing the change and processing of the optical power.

After receiving the discovery response message of the newly added ONU through the set-top message, the OLT sends a ranging request message to start the ranging process of the newly added ONU, and after receiving the ranging start message, the ONU replies the ranging response message through a set-top mechanism under the condition of not stopping high-speed data of other ONUs, and puts the processing delay information of the related ONU into the response ranging message.

The OLT can calculate the distance between the ONU and the OLT according to the sending time of the ranging request message, the receiving time of the ranging response message, the processing delay information of the ONU and other relevant parameters. The discovery and ranging procedures of the ONU may be combined.

The optical power of the channel-modulated signal is adjusted by the optical power monitoring function of the OLT, and in order to reduce the influence of channel-modulated signal superposition on high-speed broadband data as much as possible, the optical power level adjustment function of the PON can be utilized to adjust the optical power of the channel-modulated signal of the newly added ONU through the frame structure OAM of a high-speed data frame or the ONU informed by the channel-modulated signal of the OLT.

Because the optical power of the pilot tone is relatively weak, the rate of pilot tone design is low for ease of processing. In order to solve the problem that the equalization delay error is relatively large due to ranging of low-rate data, after ranging is completed, a preamble of relatively large uplink physical layer overhead (PLOu) is set, and taking the tuning hardware rate as 1Mbps as an example, a hardware circuit is set to be capable of distinguishing 10% (10MHz) pulses, so that about 16 bytes of preamble are required to be added for a 1.25G uplink rate (taking GPON or EPON as an example), namely, (1.25G/10M)/8 is 15.625, and the whole is 16 Byte; if the setup hardware circuitry is set to resolve 2% (50MHz) bursts, then a 10G upstream rate (in the example of XGS-PON) requires the addition of about 25 bytes of preamble, i.e., (10G/50M)/8 ═ 25, rounded to 25 bytes. And then, the number of lead code bytes is gradually reduced by matching with the phase monitoring and balanced delay updating functions of the OLT, so that the physical layer overhead is reduced, and the bandwidth utilization rate of uplink data is improved.

The ranging algorithm involved in the invention can be specified by reference to ITU-G.984.3, and the ranging algorithm is not described in detail in the invention.

Example 3

As shown in fig. 4, a method for discovering and ranging an ONU in a TDM PON according to an embodiment of the present invention includes:

step S101: and the uplink and downlink data transmission of the online ONU is not stopped. The networking of the devices is as in figure 1.

Step S102: and the OLT allocates uplink data transmission time slots of the on-line ONUs.

And S103, the OLT monitors and records the optical power corresponding to the uplink data of each online ONU according to the distributed uplink data sending time slot of the ONU.

And step S104, the optical power corresponding to each on-line ONU monitored by the OLT is in a stable state.

Step S105: as shown in fig. 3, the OLT periodically starts a discovery command, superimposes the discovery command, the ranging command, and a tune-to-top signal on the high-speed data channel and broadcasts according to whether a new ONU is added to transmit a ranging command. The sending mode can also be a traditional frame structure OAM high-speed data frame structure broadcast channel of the TDM PON.

Step S106: and if the newly added ONU exists, the ONU carries out discovery and ranging response.

Step S107: and the OLT carries out decoding and distance calculation according to the received optical power change of each online ONU. And if the monitored optical power is abnormal, continuously sending a new tuning signal until the monitored optical power is normal. If the ranging is not completed within one cycle, waiting until the next cycle, S105 to S107 are re-executed to perform the ranging again. If ranging is completed within one period, the process proceeds to step S108.

If the optical power of the top-tuning signal of the ONU is too small, the decoding of the top-tuning signal cannot be completed or the decoding error code is large, which means that the top-tuning optical power is abnormal. The abnormal top-adjusting optical power can cause that the ONU can not normally receive the response message of the OLT (because the OLT can not receive the top-adjusting message of the ONU, the ONU can not respond), at the moment, the top-adjusting sending end of the ONU is required to adjust the optical power of the top-adjusting signal within a certain range, the optical power of the top-adjusting signal is gradually increased within the optical power allowable range according to the OLT, and then the ONU sends a message to the OLT until the ONU receives the normal response message of the OLT.

Step S108: the new ONU completes the joining.

In summary, the present invention completes discovery and ranging of a newly added ONU without turning off an on-line ONU uplink transmitter, and implements synchronous ranging and data transmission.

Example 4

As shown in fig. 5, the present invention provides an ONU discovery ranging system in a TDM PON, including an OLT device and an ONU device, where the ONU device includes a set-top-sending subunit, and the OLT device includes a set-top-receiving subunit, where:

the OLT broadcasts a discovery request message to the on-line ONU and the newly added ONU by utilizing a traditional high-speed data frame structure OAM;

And the optical power of the tuning-top signal of the discovery response message and the ranging response message of the newly added ONU is superposed on the optical power of the ONU which is carrying out high-speed data transmission on line without influencing the high-speed data transmission.

Example 5

Further, as shown in fig. 6, the ONU further includes a set-top receiving subunit, and the OLT further includes a set-top transmitting subunit, where:

and the top-tuning receiving subunit of the ONU is used for receiving the discovery request message.

Further, the discovery request message includes an initial optical power of the tune-to-tune signal.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, a device embedded processor, or other programmable apparatus. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

In some of the flows described in the present specification and claims and in the above-described figures, a number of operations are included that occur in a particular order, but it should be clearly understood that these operations may be performed out of order or in parallel as they occur herein, the order of the operations merely being used to distinguish between the various operations, and the order of execution does not itself represent any order of execution. Additionally, the flows may include more or fewer operations, and the operations may be performed sequentially or in parallel.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. An ONU discovery ranging method in a TDM PON, the method comprising:

after receiving the discovery response message, the OLT determines a corresponding newly-added ONU according to the discovery response message and sends a ranging request message to the newly-added ONU; after receiving the discovery response message, the OLT determines a corresponding newly added ONU according to the discovery response message, which specifically includes: the OLT determines that a newly added ONU exists by comparing the optical power of the superposed pilot tone signal with the previously recorded optical power change when the pilot tone signal is not superposed and performing decoding and message interaction, and determines the ONU ID of the newly added ONU through message interaction;

2. The ONU discovery ranging method in a TDM PON of claim 1, wherein said OLT broadcasts a discovery request message to an on-line and newly-added ONU, specifically:

3. The ONU discovery ranging method in a TDM PON according to claim 1 or 2, wherein the OLT discovery request message is transmitted by a tune-up modulation based on the high-speed transmission data of the OLT; and the optical power of the tuning signal of the discovery response message and the ranging response message of the newly added ONU is superposed on the optical power of the ONU which is carrying out high-speed data transmission on line.

4. The method according to claim 3, wherein a discovery request message sent by the OLT includes an initial optical power of a set-top signal, and the initial optical power of the set-top signal specifically is: and calculating the maximum optical power allowed by the tuning signal by monitoring the receiving optical power of each on-line ONU on the OLT, and informing the ONU as the initial optical power.

5. The method for ONU discovery ranging in a TDM PON of claim 3, further comprising:

and adjusting the optical power of the newly added ONU by using the optical power level adjusting function of the PON through the ONU notified by the top-adjusting signal of the high-speed data frame or the frame structure OAM of the OLT.

6. The method for ONU discovery ranging in a TDM PON of claim 1 or 2, further comprising: after ranging is completed, a lead code with relatively large uplink physical layer overhead is set, and the number of lead code bytes is gradually reduced by matching with the phase monitoring and balanced delay updating functions of the OLT.

7. An ONU discovery ranging system in a TDM PON, comprising an OLT device and an ONU device, wherein the ONU comprises a set-top-sending subunit, and wherein the OLT comprises a set-top-receiving subunit, wherein:

the top-tuning receiving subunit of the OLT is configured to receive the discovery response message, and the OLT is configured to determine a corresponding newly added ONU according to the discovery response message and send a ranging request message to the newly added ONU; after receiving the discovery response message, the OLT determines a corresponding newly added ONU according to the discovery response message, which specifically includes: the OLT determines that a newly added ONU exists by comparing the optical power of the superposed pilot tone signal with the previously recorded optical power change when the pilot tone signal is not superposed and performing decoding and message interaction, and determines the ONU ID of the newly added ONU through message interaction;

8. The ONU discovery ranging system in a TDM PON of claim 7, wherein the ONU further comprises a set-top receiving sub-unit, wherein the OLT further comprises a set-top transmitting sub-unit, wherein:

9. The ONU discovery ranging system in a TDM PON of claim 7 or 8, wherein the discovery request message sent by the OLT is transmitted by a tune-up modulation based on the high-speed transmission data of the OLT; and the optical power of the tuning signal of the discovery response message and the ranging response message of the newly added ONU is superposed on the optical power of the ONU which is carrying out high-speed data transmission on line.