KR100932899B1 - Wavelength independent independent downlink optical transmission apparatus and method in optical fiber termination system of WMD-POON - Google Patents

Abstract

The present invention uses a separate multi-wavelength light source (MWS) or a broadband light source (BLS) in an optical path termination system (OLT) of a WDM-based passive optical subscriber network (WDM-PON) and thus corresponds to a wavelength independent light source. By using an optical transmitter, the OLT system can be efficiently managed at low cost.

Description

Method and Apparatus for downstreaming of optical transmission regardless of wavelength in Wavelength Division Multiplexed Passive Optical Networks}

The present invention relates to a downlink optical transmission device and a method using a wavelength independent light source in a WDM passive optical subscriber network. More specifically, the present invention uses a separate multi-wavelength light source (MWS) or broadband light source (BLS) in a WDM-based passive optical subscriber network (WDM-PON) optical path termination system (OLT) and thus wavelength independent light source. A device and method for downlink optical transmitter using wavelength independent light source in WDM passive optical subscriber network that can efficiently manage, operate and maintain OLT system by using low cost optical transmitter. will be.

Recently, in preparation for the activation of voice / data / broadcasting convergence services, research and development on the Wavelegth Division Multiplexing (WDM) based subscriber network has been actively conducted worldwide.

Among the various WDM-PON structures proposed so far, the downlink optical signal recycling method uses a wavelength splitter and a combiner having one wavelength band because the uplink and downlink wavelengths are the same by recycling the downlink optical signal to form an uplink optical signal. It can be used, and also can be configured in a multi-stage remote node is possible to configure a variety of subscriber networks.

However, in such a conventional downlink optical signal recycling type WDM-PON structure, a wavelength fixed optical transmitter using a wavelength fixed light source (for example, a DFB-LD that outputs a single optical wavelength, wavelength fixed external resonance) in a telephone station to be used. Since a laser, a vertical emission laser (VCSEL), and the like are used, different types of optical transmitters are required for the number of wavelengths used by the telephone company (as the number of WDM channels).

The production, installation, and management of such light sources by wavelength act as a huge economic burden for both users and operators, resulting in a rise in system prices. That is, in the conventional downlink optical signal recycling type WDM-PON there is an inventory management problem that must have different types of optical transmitters for system operation, management, replacement in case of failure.

In the present invention, in order to solve the above problems, a separate multi-wavelength light source (MWS) or a broadband light source (BLS) is used in the optical path termination system (OLT) of the WDM-based passive optical subscriber network, and accordingly, the wavelength independent light source is used. By using the corresponding optical transmitter, the management, operation, and maintenance of the OLT system is performed at low cost.

In a preferred embodiment of the present invention, the downlink optical transmission device in the optical path termination system of the WDM-PON includes a multi-wavelength optical signal generator for generating a multi-wavelength optical signal; A demultiplexer for separating the multi-wavelength optical signal for each wavelength; An optical transmitter for receiving respective optical signals separated by wavelengths and generating respective downlink optical signals through a wavelength independent semiconductor optical amplifier wavelength independent semiconductor optical amplifier; and a multiplexer for multiplexing the transmitted downlink optical signals; It includes.

In another preferred embodiment of the present invention, the downlink optical transmission device in the optical fiber termination system of the WDM-PON includes: a wideband optical signal generator for generating a wideband optical signal; A demultiplexer for separating the wideband optical signal for each wavelength; An optical transmitter for receiving respective optical signals separated by wavelengths and generating respective downlink optical signals through a wavelength independent semiconductor optical amplifier wavelength independent semiconductor optical amplifier; and a multiplexer for multiplexing the transmitted downlink optical signals; It includes.

In another preferred embodiment of the present invention, the downlink optical transmission method in the optical fiber termination system of the WDM-PON includes: generating a multi-wavelength optical signal; A demultiplexing step of separating the multi-wavelength optical signal for each wavelength; An optical transmission step of receiving respective optical signals separated by wavelengths and generating respective downlink optical signals through a wavelength independent semiconductor optical amplifier and a wavelength independent semiconductor optical amplifier; and multiplexing the transmitted downlink optical signals; It includes.

In another preferred embodiment of the present invention, the downlink optical transmission method in the optical fiber termination system of the WDM-PON includes the steps of: generating a wideband optical signal; A demultiplexing step of separating the wideband optical signal for each wavelength; An optical transmission step of receiving respective optical signals separated by wavelengths and generating respective downward optical signals through a wavelength independent semiconductor optical amplifier wavelength independent semiconductor optical amplifier; and a multiplexing step of multiplexing the downwardly transmitted optical signals It includes;

The present invention manages an article in an OLT by inserting a multi-wavelength light source (MWS) or a broadband light source (BLS) into an OLT system and thus using a wavelength independent semiconductor optical amplifier without using a wavelength fixed type as an OLT optical transmitter. There is an advantage in solving the problem.

In addition, in an example of using the multi-wavelength light source in the present invention, the wavelength of the output light wavelength is smaller than the passband of the multiplexer or demultiplexer so that a plurality of wavelengths per WDM channel exist, thereby solving the wavelength stability problem of the multi-wavelength light source and system stability Has the effect of increasing.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a block diagram of a WDM passive optical subscriber network (WDM-PON) according to a conventional downlink light recycling method.

WDM-PON (WDM-PON) is largely divided into optical line terminal system (OLT: 100), optical path 110, wavelength multiplexer / demultiplexer 120, and optical subscriber device (ONU) : Optical Network Unit (130).

The optical line termination system (OLT) 100 in the telephone company office includes a protocol processing unit 101, a wavelength fixed optical transmitter (Tx # 1 to Tx #N) 102, a wavelength, as shown in the figure. And a multiplexer 103, an optical circulator 104, a wavelength demultiplexer 105, and an optical receiver 106.

When the downlink electric signal is transmitted from the protocol processing unit 101 to the plurality of wavelength fixed optical transmitters (Tx # 1 to Tx #N) 102, each wavelength fixed optical transmitter 102 may receive light corresponding to the input electrical signal. Output the signal.

The optical signals output from the wavelength fixed optical transmitter 102 are combined by the wavelength multiplexer 103, and then the optical multiplexer 115, the wavelength multiplexer / demultiplexer 120 (wavelength multiplexer / reverse) at a remote node. The multiplexer acts as a wavelength demultiplexer for the downlink signal and a wavelength multiplexer for the uplink signal) and is separated by wavelength.

The optical signal separated by wavelength in the wavelength multiplexer / demultiplexer 120 is then transmitted to the corresponding ONU 130.

In the WDM-PON structure of such a downlink light signal recycling system, an optical transmitter in a telephone company uses a "wavelength fixed optical transmitter" as a wavelength fixed light source. Examples of conventional wavelength fixed optical transmitters include DFB-LDs that output a single wavelength, wavelength fixed external resonant layers, and vertical surface emitting lasers (VCSELs).

By using the wavelength-fixed optical transmitter, the use of the above technique requires different kinds of optical transmitters as many as the number of wavelengths used by the telephone company (as the number of WDM channels).

Therefore, the production, installation, and management of light sources for each wavelength act as a huge economic burden for both users and operators, resulting in an increase in system prices, and having different types of optical transmitters for system operation, management, and replacement in case of failure. There is an inventory problem that must be done.

2 is a block diagram of a downlink optical transmission device in the optical fiber termination system of the WDM-PON as a preferred embodiment of the present invention.

In a WDM-based passive optical network (hereinafter, referred to as 'WDM-PON'), communication between a central base station and a subscriber is performed using a specific wavelength determined for each subscriber. In WDM-PON, dedicated wavelength is used for each subscriber, so it has excellent security, high capacity communication service, and different transmission technology (for example, link rate, frame format, etc.) for each subscriber or service. Has

However, as shown in FIG. 1, the downlink optical signal recycling method using the advantages of the WDM-PON requires a different type of optical transmitter as many as the number of wavelengths used by the telephone company (as much as the number of WDM channels). have.

In the present invention, the above problem is solved by the following method. The first method solves this problem by using a wavelength independent light source in the multi-wavelength light source (MWS) module and the optical transmitter 230. Next, the wavelength-independent light source is used in the broadband light source (BLS) module and the optical transmitter 230. This will be described in more detail.

Both methods demultiplex 221 the optical signal output from a multi-wavelength light source (MWS) module or a broadband light source (BLS) module for each WDM channel and then transmit the signal to an optical transmitter 230 using a wavelength independent semiconductor amplifier. The optical transmitter 230 generates a downlink optical signal from the received signal, multiplexes the wavelength 222, and transmits it to the subscriber side.

In a preferred embodiment of the present invention, the downlink optical transmitter 200 in the optical path termination system of the WDM-PON includes a multi-wavelength optical signal generator 210, a demultiplexer 221, an optical transmitter 230, and multiplexing. Part 222 is included.

The multi-wavelength optical signal generator 210 generates a multi-wavelength optical signal through the multi-wavelength light source MWS. Examples of the multi-wavelength light source include an erbium-doped fiber annular laser or a semiconductor integrated multi-wavelength laser. An example of an output spectrum output from the multi-wavelength optical signal generator is shown in FIG. 3A.

The total bandwidth generated by the multi-wavelength optical signal generator (BW _{MWS ,} FIG. 3A 300) is the number of channels (N) used in the WDM-PON and the output optical signal interval (Δλ _WDM ) 301 of the multi-wavelength optical signal generator. Must be at least as large as The expression is as follows.

BW _MWS ≥N * Δλ _WDM

The demultiplexer 221 separates the multi-wavelength optical signal received from the multi-wavelength optical signal generator 210 for each wavelength.

The optical transmitter 230 receives the optical signals separated for each wavelength by the demultiplexer 221 and then receives the downlink electrical signal from the protocol processor (see FIGS. 1 and 101). An optical amplifier generates each downward optical signal.

The multiplexer 222 generates the WDM downlink optical signal by combining the downlink transmitted optical signal. The combined downlink optical signal is transmitted to the ONU side through an optical circulator corresponding to the branching means.

Δλ _WDM <Δλ _passband

As shown in Equation 2, the output optical signal spacing Δλ _WDM 311 of the multi-wavelength optical signal generator 210 is a _passband Δλ _passband of the demultiplexer 221 and the multiplexer 222 ( Smaller than 312) (see FIG. 3B).

As a specific example, when several wavelengths exist within one channel of the WDM under conditions satisfying Equation 1 and Equation 2, a power penalty may occur due to a distortion of the downlink optical signal due to fiber dispersion during long distance transmission. .

For example, when the demultiplexer multiplexer has a wavelength interval of 200 GHz, the _passband Δλ _passband is preferably 1.2 nm or less. However, in this case, at least one or more optical wavelengths may exist within the passband range, but two or more are preferable.

In another preferred embodiment of the present invention, the downlink optical transmitter in the optical fiber termination system of the WDM-PON includes a broadband optical signal generator (not shown), a demultiplexer, an optical transmitter, and a multiplexer.

The broadband optical signal generator generates a broadband optical signal through the broadband light source BLS. Examples of the broadband light source BLS include a semiconductor SLD (Superluminescent LED), an erbium-added optical fiber amplifier ASE (Amplified Spontaneous Emission) light source, and a semiconductor optical amplifier ASE light source.

In another embodiment, since the functions of the demultiplexer, the optical transmitter, and the multiplexer are the same as or similar to those of the corresponding components described in the parts described with reference to FIG. See the description for one embodiment.

3 a to 3 c show the output spectrum of a multi-wavelength light source, the pass band of the demultiplexer / multiplexer and the output spectrum after passing the demultiplexer / multiplexer in the structure according to the embodiment of the present invention with reference to FIG. .

3A illustrates an output spectrum of a multi-wavelength optical signal generated by the multi-wavelength optical signal generator 210. As can be seen in the figure, a plurality of multi-wavelength optical signals are output, and the output optical power of each wavelength is uniform within 5 dBm.

3B shows a passband of the demultiplexer and the multiplexer.

As shown in FIG. 3B, the WDM channel pass bandwidth Δλ _passband in the demultiplexer and the multiplexer is the output wavelength interval Δλ _WDM of the multi-wavelength optical signal generated by the multi-wavelength optical signal generator 210. It is preferable that it is above.

3C shows the output spectrum for a particular channel after passing through the demultiplexer and the multiplexer.

When the relationship as shown in Equations 1 and 2 holds, the spectrum after finally passing through the multiplexing unit in the downlink optical transmitter of the present invention using the multi-wavelength light source is as shown in FIG. 3C.

That is, the multi-wavelength light source shown in the _passband Δλ _passband 321 after passing through the demultiplexer and the multiplexer among the multi-wavelength optical signals generated by the multi-wavelength optical signal generator 210 is shown.

4 shows an embodiment of an optical fiber termination system using a downlink transmission apparatus as a preferred embodiment of the present invention.

The optical fiber termination system (OLT) 400 includes a protocol processor 410, a downlink transmitter 420, an uplink optical receiver 430, and an optical circulator 440.

The protocol processor 410 performs a function of protocol processing the downlink electrical signal to be transmitted to the subscriber or the uplink electrical signal transmitted from the subscriber.

As shown in FIG. 2, the downlink transmitter 420 includes a multi-wavelength optical signal generator 421, an optical circulator 422, a demultiplexer and a multiplexing module 423, and a wavelength independent optical receiver 424. It includes.

When the multi-wavelength optical signal is output from the multi-wavelength optical signal generator 421 of the downlink transmitter 420, the optical circulator 422 transmits the multi-wavelength optical signal to the demultiplexer and the multiplexing module 423. The demultiplexer and the multiplexing module 423 separate the transmitted multi-wavelength optical signals by wavelengths (see FIG. 3B) and output them to the respective optical transmitters 424 (see FIG. 3C).

 Here, the demultiplexer and the multiplexing module 423 operate as a demultiplexer corresponding to the wavelength divider for the multi-wavelength optical signal output from the multi-wavelength optical signal generator 421 and input through the optical circulator 422. The optical signal input from the optical transmitter 424 operates as a wavelength multiplexer.

Subsequently, when the optical transmitter 424 receives the downlink electric signal from the protocol processor 410, the downlink optical signal is generated and output by using the input optical signal.

The demultiplexer and multiplexer module 423 combines the downlink optical signal output from the optical transmitter 424 to operate as a wavelength multiplexer to generate a WDM downlink optical signal. The combined downlink optical signal is transmitted to the ONU side through optical circulators 422 and 440 corresponding to the branching means.

Meanwhile, the upward optical receiver 430 includes a wavelength demultiplexer 431 and a plurality of optical receivers (PDs) 432. The WDM uplink optical signal transmitted from the optical circulator 440 (the optical signal transmitted from the ONU side) is separated for each wavelength, and each optical signal is converted into an electrical signal and output to the protocol processor 410. .

The optical network unit (ONU) 450 includes a tap coupler 451, an optical transmitter 452, an optical receiver 453, and a protocol processing unit 454. . Here, the optical transmitter 452 is a wavelength independent semiconductor optical amplifier. That is, in the present invention, both the ONU and the OLT optical transmitter use a wavelength independent semiconductor optical amplifier.

The tap coupler 451 transmits a part of the downlink optical signal transmitted from the wavelength demultiplexer 431 to a photo diode (PD # 1) 453 to restore the downlink signal. The other part is injected into the optical transmitter (Tx # 1) 452.

Subsequently, when the optical transmitter (Tx # 1) 452 receives an upward electric signal from the protocol processor 454 inside the ONU 450, the optical transmitter (Tx # 1) 452 recycles the downward optical signal injected by the tap coupler 451. The uplink optical signal is formed and transmitted.

The optical transmitter 452 of the ONU 450 does not have an inventory problem by using a semiconductor optical amplifier which is a wavelength independent light source, and can accommodate all WDM channels as a single type of optical transmitter.

FIG. 5 shows another embodiment of the optical fiber termination system using the downlink transmission apparatus as another preferred embodiment of the present invention.

The embodiment of FIG. 5 converts the multi-wavelength optical signal generator 421 into the wideband optical signal generator 521 in FIG. 4, and considers a portion of a downlink transmitter using the wideband optical signal generator 521. Other components will be referred to the above description.

The downlink transmitter 520 includes a wideband optical signal generator 521, an optical circulator 522, a demultiplexer and a multiplexing module 523, and a wavelength independent optical receiver 524.

The broadband optical signal generator 521 is a broadband optical signal using a broadband light source (BLS) such as a semiconductor SLD (Superluminescent LED), an erbium-added optical fiber amplifier ASE (Amplified Spontaneous Emission) light source, or a semiconductor optical amplifier ASE light source. Create An example 600 of the broadband light source output spectrum of the broadband optical signal generator 521 is illustrated in FIG. 6A.

The output bandwidth (BW _BLS ) 600 of the wideband optical signal generator 521 should satisfy the following equation when the number of channels N used in the WDM-PON and the channel spacing are Δλ _WDM .

BW _BLS ≥N * Δλ _WDM

When Equation 3 is satisfied, when the multi-wavelength optical signal is output from the multi-wavelength optical signal generator 521 of the downlink transmitter 420, the optical circulator 522 demultiplexes the wideband optical signal and the multiplexing module 523. ). The demultiplexer and the multiplexing module 523 separate the transmitted multi-wavelength optical signals by wavelengths (see FIG. 6B) and output them to the respective optical transmitters 524 (see FIG. 6C).

As shown in FIG. 6B, the bandwidth after passing the demultiplexer and the multiplexing module 523 is determined by the channel _passband Δλ _passband 612 of the demultiplexer and the multiplexing module 523. Δλ _{passband for} long distance transmission to reduce penalty It is preferable that silver is 1.2 nm or less.

Here, the demultiplexer and the multiplexing module 523 operate as the demultiplexer corresponding to the wavelength divider for the multi-wavelength optical signal output from the multi-wavelength optical signal generator 521 and input through the optical circulator 522. The optical signal input from the optical transmitter 524 operates as a wavelength multiplexer.

Subsequently, when the optical transmitter 524 receives the downlink electrical signal from the protocol processor, the optical transmitter 524 generates and outputs the corresponding downlink optical signal by using the input optical signal. The demultiplexer and multiplexer module 523 combines the downlink optical signal output from the optical transmitter 524 to operate as a wavelength multiplexer to generate a WDM downlink optical signal. The combined downlink optical signal is transmitted to the ONU side through an optical circulator corresponding to the branching means.

6a to 6c show the output spectrum of the broadband light source, the pass band of the demultiplexer / multiplexer and the output spectrum after passing the demultiplexer / multiplexer in the structure according to the embodiment of the present invention with reference to FIG. .

6A illustrates a broadband light source output spectrum of a broadband optical signal generator of a downlink optical transmitter using the broadband light source shown in FIG. 5 as a preferred embodiment of the present invention.

FIG. 6B illustrates a channel passband (Δλ _{p assba nd} ) 612 in the demultiplexer and the multiplexing module of the downlink optical transmitter using the broadband light source shown in FIG. 5 as a preferred embodiment of the present invention.

FIG. 6C shows a spectrum after passing through the demultiplexing unit and the multiplexing module of the downlink optical transmitter using the broadband light source shown in FIG. 5 as one preferred embodiment of the present invention. In this case, the channel _passband Δλ _passband is equal to 620.

The invention can also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). It also includes. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

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

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

1 is a block diagram of a WDM passive optical subscriber network (WDM-PON) according to a conventional downlink optical signal recycling method.

2 is a block diagram of a downlink optical transmission device in the optical fiber termination system of the WDM-PON as a preferred embodiment of the present invention.

3 a to 3 c show the output spectrum of a multi-wavelength light source, the pass band of the demultiplexer / multiplexer and the output spectrum after passing the demultiplexer / multiplexer in the structure according to the embodiment of the present invention with reference to FIG. .

FIG. 4 shows an embodiment of the optical fiber termination system using the downlink transmission apparatus of FIG. 2 as a preferred embodiment of the present invention.

FIG. 5 shows another embodiment of the optical fiber termination system using the downlink transmission apparatus as another preferred embodiment of the present invention.

6a to 6c show the output spectrum of the broadband light source, the pass band of the demultiplexer / multiplexer and the output spectrum after passing the demultiplexer / multiplexer in the structure according to the embodiment of the present invention with reference to FIG.

Claims (19)

WDM-PON wavelength independent optical downlink transmitter in optical fiber termination system A multi-wavelength optical signal generator for generating a multi-wavelength optical signal; A demultiplexer for separating the multi-wavelength optical signal for each wavelength; An optical transmitter for receiving respective optical signals separated by wavelengths and generating respective downward optical signals through a wavelength independent semiconductor optical amplifier; and And a multiplexer for multiplexing the downlinked optical signal, wherein the optical subscriber unit (ONU) in the optical path termination system of the WDM-PON uses a wavelength independent semiconductor optical amplifier in the downlink optical transmitter. And an optical transmitter for forming and transmitting a portion of the transmitted downlink signal as an uplink optical signal. The method of claim 1, wherein the multi-wavelength optical signal generation unit Downlink optical transmission device, characterized in that for generating the multi-wavelength optical signal through a multi-wavelength light source (MWS). The method of claim 2, wherein the multi-wavelength light source An erbium-doped fiber annular laser or a semiconductor integrated multi-wavelength laser, characterized in that the downlink optical transmission device. The method of claim 1, The total bandwidth (BW _MWS ) generated by the multi-wavelength optical signal generator is Downlink optical transmission device, characterized in that more than the magnitude of the product between the number of channels (N) used in the WDM-PON and the output optical signal interval (Δλ _WDM ) of the multi-wavelength optical signal generator. The method of claim 1, And an output optical signal interval Δλ _{WDM of} the multi-wavelength optical signal generator is smaller than a _passband Δλ _passband of the demultiplexer and the multiplexer. delete WDM-PON wavelength independent optical downlink transmitter in optical fiber termination system A wideband optical signal generator for generating a wideband optical signal; A demultiplexer for separating the wideband optical signal for each wavelength; An optical transmitter for receiving respective optical signals separated by wavelengths and generating respective downward optical signals through a wavelength independent semiconductor optical amplifier; and And a multiplexer for multiplexing the downlinked optical signal, wherein the optical subscriber unit (ONU) in the optical path termination system of the WDM-PON includes an optical transmitter, and the optical transmitter includes a wavelength independent semiconductor light. And a part of the downlink signal transmitted from the downlink optical transmitter by using an amplifier to form an uplink optical signal and transmit the uplink optical signal. The optical signal generating unit of claim 7, wherein the wideband optical signal generator Downlink optical transmission device characterized in that for generating the wideband optical signal through a broadband light source (BLS). The method of claim 8, wherein the broadband light source (BLS) is A downlink optical transmitting device, characterized in that it is one of a semiconductor SLD (Superluminescent LED), an Erbium-added optical fiber amplifier (ASE) light source, or a semiconductor optical amplifier ASE light source. The method of claim 7, wherein The total bandwidth (BW _BLS ) generated by the wideband optical signal generator is Downlink optical transmission device, characterized in that more than the magnitude of the product between the number of channels (N) used in the WDM-PON and the channel interval (Δλ _WDM ) of the WDM-PON. delete The method according to claim 1 or 7, And a branching unit configured to transfer the generated optical signal to the demultiplexer or to transmit an output optical signal of the multiplexer to a subscriber side. As a wavelength independent downlink optical transmission method in a WDM-PON optical fiber termination system, Generating a multi-wavelength or wideband optical signal; A demultiplexing step of separating the multi-wavelength or broadband optical signal by wavelength through a demultiplexer; An optical transmission step of receiving respective optical signals separated by wavelengths and generating respective downward optical signals through a wavelength independent semiconductor optical amplifier; and Multiplexing the downwardly transmitted optical signal through a multiplexer, wherein the optical subscriber unit (ONU) in the optical fiber termination system of the WDM-PON includes an optical transmitter, and the optical transmitter is wavelength independent And a part of the downlink signal transmitted from the downlink optical transmitter by using a semiconductor optical amplifier to form and transmit an uplink optical signal. The method of claim 13, The multi-wavelength optical signal is generated by a multi-wavelength light source (MWS) And a broadband optical signal is generated through a broadband light source (BLS). The method of claim 14, The multi-wavelength light source is an erbium-doped fiber annular laser or a semiconductor integrated multi-wavelength laser The broadband light source (BLS) is one of a semiconductor superlumimescent LED (SLD), an erbium-added optical fiber amplifier ASE (Amplified Spontaneous Emission) light source, or a semiconductor optical amplifier ASE light source, characterized in that one. The method of claim 13, The total bandwidth generated in the multi-wavelength optical signal generation step is And the number of channels used in the WDM-PON and the magnitude of the product between the output optical signal intervals generated in the multi-wavelength optical signal generation step. The method of claim 13, And the output optical signal interval in the optical signal generating step is smaller than the pass bandwidth used in the demultiplexing step and the multiplexing step. delete The method of claim 13, And transmitting the generated optical signal to the demultiplexer or transferring the output optical signal of the multiplexer to a subscriber side.

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