KR101231927B1 - Bidirectional WDM-PON system using single channel and bidirectional signal transmitting method thereof - Google Patents

Abstract

The present invention discloses a WDM-PON system that enables transmission of up and down signals using a single channel.

The WDM-PON system of the present invention modulates a light source having the same wavelength into an uplink subcarrier and a downlink signal, respectively, and then modulates the uplink subcarrier and the downlink signal to transmit the light through the optical path as a downlink light and receive the light through the optical path. A telephone station apparatus for recovering an uplink signal from the uplink light; A subscriber device for restoring a downlink signal from the downlink signal light among the downlink light, and modulating the downlink light and transmitting the downlink light as an uplink light; And a remote node for wavelength-separating the downlink light from the telephone station apparatus and transmitting it to the subscriber apparatus, and for transmitting the uplink light from the subscriber apparatus to wavelength division multiplexing and transmitting it to the telephone station apparatus. By enabling downlink signal transmission, the network structure can be configured more flexibly.

Description

Bidirectional WDM-PON system using single channel and bidirectional signal transmitting method, which enables transmission of uplink and downlink signals using a single channel

Figure 1 is a schematic diagram showing the configuration of a conventional WDM-PON system for supplying the light source of each subscriber from the telephone station.

2 is a system configuration diagram showing the configuration of the WDM-PON system according to the present invention.

)의 주파수 스펙트럼을 보여주는 도면.3 shows a light source before and after being modulated by an external modulator (

Diagram showing the frequency spectrum of the circuit.

)의 주파수 스펙트럼을 보여주는 도면.4 shows light coupled by an optical coupler (

Diagram showing the frequency spectrum of the circuit.

5 is a view showing in more detail the structure and operation of the OLT transmitter in the OLT of FIG.

6 is a configuration diagram showing in more detail the configuration and operation of the ONU receiver in FIG.

7 is a view showing in more detail the structure and operation of the ONU transmitter provided in the ONU of FIG.

FIG. 8 is a diagram illustrating the configuration and operation of an OLT receiver receiving an uplink signal in the OLT of FIG. 2 in more detail. FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

10: light source providing unit 12: laser diode

14, 42, 46, 50: WDM 16, 24, 30, 62: optical splitter

22: external modulator 41, 45: optical circulator

43, 66: R-SOA transmitter 47, 64: receiver

The present invention relates to a Wavelength Division Multiplexing-Passive Optical Network (WDM-PON) system in which a light source of each subscriber is supplied from a telephone station, and more specifically, a subcarrier (sub) The present invention relates to a WDM-PON system and a method for transmitting the same, which enable transmission of uplink and downlink signals through a single channel using a carrier.

Recently, passive optical subscriber networks have been actively studied to expand the capacity and speed of transmission of broadband subscriber networks. Among these PON technologies, WDM-PON is attracting attention as a next-generation technology that makes it possible to easily configure a large capacity subscriber network using the broadband characteristics of optical fibers.

WDM-PON is a passive optical device that connects the optical line terminal (OLT) and optical network unit (ONU) of a central office (CO), a telecommunications service provider, with passive optical devices. It is a network that distributes and transmits the signals to each ONU.

As such, when the ONU is connected to the telephone station by using optical fiber, there is a big advantage to reduce the installation cost of the ONU by concentrating the signal processing device on the telephone station. The method is proposed.

Figure 1 is a schematic diagram showing the configuration of a conventional WDM-PON system for supplying the light source of each subscriber from the telephone station.

)을 제공하면, 가입자측의 지역 기지국(RN:Remote Node)에 구비되어 있는 WDM 다중화/역다중화(이하, WDM 이라 함)에서 각 가입자별로 파장을 분리하여 ONU로 전송한다. 파장이 분리된 각 광신호(

)는 ONU의 반사형 반도체 광증폭기(R-SOA)에 입사된 후 광증폭기(R-SOA)의 주입전류(신호전류)에 의해 변조된다. 변조된 가입자 신호광(

)은 WDM에서 다중화(

)되어 전화국 측으로 전송된다.Light sources of different wavelengths for each subscriber in the telephone company (

), WDM multiplexing / demultiplexing (hereinafter, referred to as WDM) provided in a local base station (RN: Remote Node) on the subscriber side separates the wavelength for each subscriber and transmits it to the ONU. Each optical signal whose wavelength is separated

) Is incident on the reflective semiconductor optical amplifier R-SOA of the ONU and then modulated by the injection current (signal current) of the optical amplifier R-SOA. Modulated subscriber signal light (

) Is multiplexed in WDM

Is sent to the telephone company.

However, in the case of the WDM-PON method in which subscriber light sources are provided by telephone stations, wavelengths of different bands are used for uplink and downlink transmission. As such, when different bands are used for uplink and downlink transmission, there are many disadvantages when adding or removing wavelengths in a multi-stage branching or ring structure network. Therefore, it is desirable to simultaneously implement uplink and downlink transmission using the same channel of WDM.

In accordance with such a requirement, many examples of simultaneously implementing uplink and downlink transmission using a single channel have been published.

1. W. Lee, et al, "Bidirectional WDM-PON based on gain-saturated semiconductor optical amplifiers", Photonic Technol. Letter, Vol. 17, No. 11, pp 2460-2462, 2005.

2. C. Arllano, et al, "R-SOA based Optical Network Units for WDM-PON", OFC / NFOEC, OTuC1, 2006.

In this case, in the case of [1], the DFB-LD is modulated by a downlink signal of about 3dB, and a part of the modulated downlink signal is used as a seed light to be modulated by an optical amplifier (R-SOA) and used as an uplink signal. use. However, this method is possible to implement bidirectional with a single wavelength, but there is a disadvantage in transmission because the modulated signal is used as a seed light source.

Also, in [2], the same wavelength is used as the up / down while comparing the performance of the method of classifying up / down by time division and the method of classifying up / down by sub-carrier multiplexing (SCM). Although the technique is disclosed, these methods have a problem that it is difficult to have a transmission rate of 1.25Gbps due to the limitation of the R-SOA modulation rate.

Therefore, an object of the present invention for solving the above-mentioned problems is to enable the up and down signal transmission using a single channel while more flexibly configuring the network structure in the WDM-PON structure that provides the subscriber light source from the telephone station.

WDM-PON system that enables the transmission of the up and down signals using a single channel of the present invention for achieving the above object, an external modulator for modulating the wavelength division multiplexed light source to generate a sub-carrier for the uplink signal; Modulating the light source to generate a downlink signal light, combining the generated downlink signal light with an uplink subcarrier from the external modulator to transmit the downlink light as a downlink light, and recovering the uplink signal from the uplink light received through the light path; OLT; An ONU receiving the wavelength-separated downlink light and restoring a downlink signal from the downlink signal light among the downlink light, modulating the downlink light, and transmitting the downlink light as the uplink light; And a WDM filter for wavelength-separating the downlink light from the OLT to the corresponding ONU and wavelength-division multiplexing the upstream light from the ONUs to the OLT.

In the WDM-PON system, which enables transmission of an uplink signal and a downlink signal using a single channel of the present invention, a modulated light source having the same wavelength into an uplink subcarrier and a downlink signal light, respectively, and modulates the modulated uplink subcarrier and the downlink signal light. A telephone station device for combining and transmitting over the optical path as a downward beam and for recovering an upward signal from the upward beam received through the optical path; A subscriber device for restoring a downlink signal from the downlink signal light among the downlink light, and modulating the downlink light and transmitting the downlink light as an uplink light; And a remote node for wavelength-separating the downlink light from the telephone station apparatus and transmitting it to the subscriber apparatus and wavelength-division multiplexing the upstream light from the subscriber apparatus to the telephone apparatus.

In the WDM-PON method of supplying a light source from a telephone station device to each subscriber device, the uplink / downlink signal transmission method using a single channel of the present invention branches the light source from the telephone station device so that the first branched light is an uplink subcarrier. A first step of modulating and modulating the second branched light into a downward signal light; A second step of combining, by the telephone station apparatus, the modulated uplink subcarrier and the downlink signal light and transmitting the downlink light to the subscriber device; A third step of the subscriber apparatus recovering a downlink signal using the downlink signal light of the downlink light, modulating the downlink light, and transmitting the downlink light to the telephone station apparatus as an uplink light; And a fourth step of recovering an uplink signal from the uplink light by using the uplink subcarrier.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a system configuration diagram showing the configuration of the WDM-PON system according to the present invention.

The WDM-PON system of the present invention includes a light source providing unit 10, an external modulator 20, an optical splitter 30, an OLT 40, a WDM filter 50, and an ONU 60 which is a subscriber device.

)들을 생성한 후 이를 파장 분할 다중화 하고 다중화된 광원(

)을 2분기하여 각각 외부 변조부(20) 및 광분기기(30)로 출력한다. 이때,

에서 i는 임의의 정수로 광원(

)은 특정된 하나의 파장을 갖는 광원을 나타내는 것이 아니라 모든 가입자 광원들을 대표하여 나타낸다. 따라서, 이후 모든 가입자 광원들은

으로 표기한다. 이러한 광원 제공부(10)는 서로 다른 파장의 광원(

)들을 생성하여 출력하는 다수의 레이저 다이오드(12), 레이저 다이오드(12)에서 출력되는 광원(

)들을 파장 분할 다중화하여 출력하는 WDM(14), WDM(14)에서 다중화된 광원(

)을 2분기하여 각각 외부 변조부(20) 및 광분기기(30)로 출력하는 광분기기(16)를 구비한다.The light source providing unit 10 includes a plurality of continuous wave laser lights (light sources) having different wavelengths assigned to each subscriber (

) And then use wavelength division multiplexing and multiplex

) Is bifurcated and output to the external modulator 20 and the optical splitter 30, respectively. At this time,

In which i is a random integer

) Does not represent a light source with one specified wavelength but represents all subscriber light sources. Thus, all subsequent subscriber light sources

Mark as. The light source providing unit 10 is a light source of different wavelengths (

) A plurality of laser diodes 12 to generate and output, the light source output from the laser diode 12 (

) WDM 14 for outputting by wavelength division multiplexing, and the light source multiplexed in WDM 14

), And the optical splitter 16 outputs to the external modulator 20 and the optical splitter 30, respectively.

)을 일정 주파수(fu)로 변조하여 상향 신호용 부반송파(Sub-carrier)(

)를 생성하고 생성된 상향 신호용 부반송파(

)를 전화국 내 다수의 OLT들에서 공통으로 사용할 수 있도록 n개의 광으로 분기하여 대응되는 OLT(40)들로 전송한다. 이러한 외부 변조부(20)는 광분기기(16)에서 분기된 광원(

)을 fu의 주파수로 변조하는 외부 변조기(22) 및 외부 변조기(22)에서 변조된 광(

)을 n개의 광으로 분기하는 광분기기(24)를 구비한다. 이때, 상향 신호용 부반송파(

)를 생성하기 위한 변조 주파수(fu)는 하향 신호의 대역폭 보다 큰 주파수가 사용된다. 도 3은 외부 변조기(22)에서 변조되기 전/후의 광원(

)의 주파수 스펙트럼을 보여주는 도면이다. 도 3a와 같이 f₁ ∼ f_m의 주파수를 갖는 다중화된 연속파 레이저광(

)은 외부 변조기(22)에 의해 fu의 주파수로 변조됨으로써 도 3b와 같은 주파수 스펙트럼을 갖는 상향 신호용 부반송파(

)로 변화된다.The external modulator 20 is a light source (1 branch of the light bi-branched in the optical splitter 16)

) Is modulated at a predetermined frequency (fu) to sub-carrier (up-signal)

) And the generated subcarrier for the uplink signal (

) Is split into n lights and transmitted to the corresponding OLTs 40 so that they can be commonly used by multiple OLTs in the telephone station. The external modulator 20 may be a light source branched from the optical splitter 16.

) Modulated light at an external modulator 22 and an external modulator 22 that modulates at a frequency of fu

) Is provided with an optical splitter 24 which splits n into n lights. At this time, the subcarrier for the uplink signal (

For the modulation frequency fu to be generated, a frequency larger than the bandwidth of the downlink signal is used. 3 shows a light source before and after being modulated by the external modulator 22 (

Is a diagram showing the frequency spectrum of the waveguide. F ₁ as shown in Figure 3a ~ Multiplexed continuous wave laser light having a frequency of f _m (

) Is modulated at the frequency of fu by the external modulator 22, so that an uplink subcarrier (i) having a frequency spectrum as shown in FIG.

).

)을 다시 n개의 광으로 분기함으로써 광원(

)이 전화국 내 복수의 OLT(40)들에서 하향 신호 전송을 위해 공통으로 사용할 수 있도록 해준다.The optical splitter 30 is a light source (1) of another branch of light split in the optical splitter 16.

) Is split into n lights again,

This allows a plurality of OLTs (40) in a telephone station to be commonly used for downlink signal transmission.

)을 반도체 광증폭기(R-SOA)를 이용하여 하향 신호광(

)으로 변조한 후 변조된 하향 신호광(

)과 외부 변조부(20)에서 변조된 상향 신호용 부반송파(

)를 결합(

)시켜 가입자측으로 전송한다. 그리고, OLT(40)는 가입자의 ONU(60)로부터의 상향 신호광을 수신하여 이를 전기신호로 변환한 후 이 중 상향 신호를 필터링함으로써 상향 신호를 복원한다. 이러한 OLT(40)는 광서큘레이터(41, 45), WDM(42, 46), OLT송신기(R-SOA)(43), 광결합기(44) 및 OLT수신기(47)를 구비한다. 광서큘레이터(41)는 광분기기(30)에서 분기되어 입력되는 광(

)을 WDM(42)으로 전송하고 WDM(42)에서 다중화되어 출력되는 하향 신호광(

)을 광결합기(44)로 전송한다. WDM(42)은 광서큘레이터(41)로부터 입력되는 광(

)을 파장별로 분리(역다중화)하여 OLT송신기(43)로 전송하고 OLT송신기(43)에서 변조된 하향 신호광(

)들을 다중화(

)하여 광서 큘레이터(41)로 전송한다. OLT송신기(43)는 입력되는 광(

)을 하향 신호전류로 변조하여 하향 신호광(

)을 생성한 후 이를 WDM(42)으로 출력한다. 광결합기(44)는 광서큘레이터(41)로부터의 하향 신호광(

)과 외부 변조부(20)로부터의 상향 신호용 부반송파(

)를 결합시켜 출력한다. 이때, 광결합기(44)에 의해 결합된 광(

)의 주파수 스펙트럼은 도 4와 같다. 광서큘레이터(45)는 광결합기(44)에서 결합된 광(

)을 WDM 필터(5)로 전송하고 WDM 필터(50)로부터 수신되는 상향 신호광(

)을 WDM(46)으로 전송한다. WDM(46)은 상향 신호광(

)을 일정 대역의 파장별로 분리하여 OLT수신기(47)로 전송한다. OLT수신기(47)는 수신된 상향 신호광(

)을 전기신호로 변환한 후 변환된 전기신호에서 상향 신호를 필터링하여 ONU(60)에서 전송한 상향 신호를 복원한다.The OLT 40 is a light source provided from the optical splitter 30

) Using a semiconductor optical amplifier (R-SOA)

Modulated with the modulated downlink signal light (

) And a subcarrier for an uplink signal modulated by the external modulator 20

)

Send it to the subscriber side. The OLT 40 receives the uplink signal light from the subscriber's ONU 60, converts the signal into an electrical signal, and restores the uplink signal by filtering the uplink signal. The OLT 40 includes optical circulators 41 and 45, WDMs 42 and 46, an OLT transmitter (R-SOA) 43, an optical coupler 44, and an OLT receiver 47. The optical circulator 41 may be configured to receive light input by being branched from the optical splitter 30.

) Is transmitted to the WDM 42 and the downlink signal light (

) Is transmitted to the optical coupler 44. The WDM 42 receives light inputted from the optical circulator 41.

) Is separated by wavelength (demultiplexed) and transmitted to the OLT transmitter 43, and the downlink signal light modulated by the OLT transmitter 43 (

Multiplexing

) To the optical circulator 41. The OLT transmitter 43 receives the input light (

) Modulates the downlink signal current so that the downlink signal light (

) And output it to the WDM 42. The optical coupler 44 receives the downlink signal light from the optical circulator 41.

) And the subcarrier for the uplink signal from the external modulator 20

) To print. At this time, the light coupled by the optical coupler 44 (

) Is shown in FIG. 4. The optical circulator 45 is coupled to the light coupled from the optical coupler 44 (

) Is transmitted to the WDM filter 5 and the uplink signal light received from the WDM filter 50 (

) Is sent to the WDM 46. The WDM 46 is an upward signal light (

) Is separated for each wavelength of a predetermined band and transmitted to the OLT receiver 47. The OLT receiver 47 receives the received uplink signal light (

) Is converted into an electrical signal, and then the upstream signal transmitted from the ONU 60 is restored by filtering the upstream signal from the converted electrical signal.

)을 일정대역의 파장별로 분리하여 분리된 광(

)을 대응되는 가입자의 ONU(60)로 전송하고, 각 가입자의 ONU(60)들에서 변조된 후 OLT(40)로 전송될 상향 광(

)들을 파장 분할 다중화하여 OLT(40)로 전송한다.WDM filter 50 is a remote node (Remonte Node) provided between the telephone station and the ONU (60), the output light of the OLT (40)

) Separated by wavelengths of a certain band

) Is transmitted to the ONU 60 of the corresponding subscriber, and modulated in the ONUs 60 of each subscriber, and then the uplink optical (to be transmitted to the OLT 40).

) Are transmitted to the OLT 40 by wavelength division multiplexing.

)을 2분기 시킨 후 분기된 광 중 1분기 광을 전기신호(광신호 전류)로 변환한 후 변환된 전기신호에서 하향 신호광에 대응되는 전기신호만을 필터링하여 하향 신호를 복원한다. 그리고, ONU(60)는 2분기된 광 중 다른 1분기 광을 반도체 광증폭기(R-SOA)를 이용하여 상향 신호광(

)으로 변조한 후 이를 WDM 필터(50)로 전송한다. 이러한 ONU(60)는 WDM 필터(50)로부터의 신호를 2분기하는 광분기기(62), 광분기기(62)에서 분기된 광을 전기신호로 변환한 후 변환된 전기신호에서 하향 신호를 필터링하여 복원하는 ONU수신기(64) 및 광분기기(62)에서 분기된 광을 상향 신호전류로 변조하여 WDM 필터(50)로 전송하는 ONU송신기(R-SOA)(64)를 구비한다.The subscriber unit ONU 60 is connected to the WDM filter 50 through one optical path and separated from the WDM filter 50.

2) and then converts the light of the first branch of the branched light into an electrical signal (optical signal current) and then filter only the electrical signal corresponding to the downlink signal from the converted electrical signal to restore the downlink signal. In addition, the ONU 60 uses the semiconductor optical amplifier R-SOA to transmit the light of the first branch of the two branched lights.

And modulate it to the WDM filter 50. The ONU 60 converts the light branched from the WDM filter 50 into the optical splitter 62 and the light splitted from the optical splitter 62 into an electrical signal, and then filters the downlink signal from the converted electrical signal. The ONU receiver 64 and the ONU transmitter (R-SOA) 64 which modulate the light branched from the optical splitter 62 into an uplink signal current and transmit the modulated light to the WDM filter 50.

5 is a view showing in more detail the structure and operation of the OLT transmitter 42 in the OLT 40 of FIG.

)을 하향 신호광으로 변조하여 송신하기 위한 수단으로 반사형 반도체 광증폭기(R-SOA)가 사용된다.In this embodiment, the laser light generated by the light source providing unit 10 (

) Is used as a means for transmitting the modulated signal to the downlink signal light.

)은 고반사 코팅막(436)에서 반사된 후 다시 활성층 도파로(432)를 통해 광도파로로 전송된다. 입사된 광(

)이 활성층 도파로(432)를 통해 진행하는 동안 도 5b에서와 같이 증폭이득(gain)이 변화되는 상향 신호전류가 기판(434)을 통해 입력됨으로써 연속파인 광(

)이 하향 신호 광(

)으로 변조된다. 이때, 본 발명에서는 하향 신호전류의 진행경로 상에 저역통과필터(LPF)(438)를 구비하여 상향 신호전류의 대역폭(bandwidth)이 f_ld 이하가 되도록 한다. 도 5c는 상술된 과정을 통해 광증폭기(43)에서 변조된 특정 주파수(f_i)의 하향 신호광(

)의 주파수 스펙트럼을 보여준다.As shown in FIG. 5A, light incident on the active layer waveguide 432 of the optical amplifier 43 after the wavelength separation at the WDM 42 is performed through the optical waveguide (

) Is reflected by the high reflection coating film 436 and then transmitted back to the optical waveguide through the active layer waveguide 432. Incident light (

5) is transmitted through the active layer waveguide 432, and as shown in FIG. 5B, an upward signal current of which amplification gain is changed is input through the substrate 434, thereby providing a continuous wave of light (

) Is the downward signal light (

Is modulated by At this time, in the present invention, a low pass filter (LPF) 438 is provided on the path of the downward signal current so that the bandwidth of the upward signal current is equal to or less than f _ld . 5C shows the downlink signal light of a specific frequency f _i modulated by the optical amplifier 43 through the above-described process (

) Shows the frequency spectrum.

Since the reflective semiconductor optical amplifier R-SOA is already widely used, a detailed description thereof will be omitted.

FIG. 6 is a diagram illustrating in more detail the configuration and operation of the ONU receiver 64 in FIG. 2.

The ONU receiver 64 includes a photodetector 642, an amplifier 644, and a low pass filter (LPF) 646.

)와 하향 신호광(

)을 전기신호(광신호 전류)로 변환하여 출력한다.The photodetector 642 is a subcarrier for an uplink signal received through an optical waveguide after being branched from the optical splitter 62.

) And downward signal light (

) Is converted into an electrical signal (optical signal current) and output.

)에 대응되는 주파수성분은 제거하고 하향 신호에 대응되는 광신호 전류만 통과시킨다.The amplifier 644 amplifies the optical signal current converted by the photodetector 642, and the low pass filter (LPF) 646 performs low pass f <f _ld pass filtering on the amplified optical signal current. Only the component corresponding to the downlink signal is passed among the optical signal currents. That is, the low pass filter (LPF) 646 transmits the light (the OLT transmitter 43). The subcarrier for the uplink signal in the optical signal current is filtered by filtering the optical signal current in the same frequency band as the frequency band f <f _ld of the downlink signal current used to modulate

The frequency component corresponding to) is removed and only the optical signal current corresponding to the downlink signal is passed.

FIG. 7 is a view showing in more detail the structure and operation of the ONU transmitter 66 provided in the ONU 60 of FIG.

)을 변조하기 위한 상향 신호전류의 대역폭(bandwidth)이 f_lu 이하가 되도록 한다.The structure and operation principle of the ONU transmitter 66 are the same as those of the OLT transmitter 43 described with reference to FIG. 5, and only the light inputted through the optical waveguide (

The bandwidth of the upstream signal current for modulating λ) is less than or equal to f _lu .

)이 광도파로를 통해서 광증폭기(66)의 활성층 도파로(662)로 입사되면, 입사된 광(

)은 고반사 코팅막(666)에서 반사된 후 다시 활성층 도파로(662)를 통해 광도파로로 전송된다. 이때, 광(

)을 변조하기 위한 상향 신호전류는 저역통과필터(LPF)(668)에 의해 대역폭(bandwidth)이 f_lu 이하로 되어 기판(664)에 입력된다.That is, as shown in FIG. 7, the light branched from the optical splitter 62 (

Is incident on the active layer waveguide 662 of the optical amplifier 66 through the optical waveguide.

) Is reflected by the high reflection coating film 666 and then transmitted back to the optical waveguide through the active layer waveguide 662. At this time,

The upstream signal current for modulating _λ is input to the substrate 664 by a low pass filter (LPF) 668 having a bandwidth of f _lu or less.

FIG. 8 is a configuration diagram illustrating in more detail the configuration and operation of the OLT receiver 47 that receives an uplink signal from the OLT 40 of FIG. 2.

The OLT receiver 47 includes a photodetector 471, an amplifier 472, a band pass filter (BPF) 473, an oscillator 474, a mixer 475, and a low pass filter (LPF) 476.

) 즉 ONU(60)의 ONU송신기(66)에 의해 상향 신호용 부반송 파(

)가 변조된 광(

)과 하향 신호광(

)이 변조된 광(

)을 전기신호(광신호 전류)로 변환하여 출력한다.Photodetector 471 is transmitted from ONU 60 to wavelength separated light at WDM 46.

I.e., the subcarrier for the uplink signal by the ONU transmitter 66 of the ONU 60

) Modulated light (

) And downward signal light (

) Modulated light (

) Is converted into an electrical signal (optical signal current) and output.

) 뿐만 아니라 하향 신호광(

)도 함께 변조하여 전송하므로 이 중에서 상향 신호용 부반송파(

)에 실린 데이터만을 추출하기 위해서 해당 대역(fu-f_lu＜f＜fu+f_lu)의 신호만을 필터링한다.The amplifier 472 amplifies the optical signal current converted by the photodetector 471, and the band pass filter (BPF) 473 is a predetermined band (fu-f _lu <f <fu + f _lu ) in the amplified optical signal current. Pass only the upstream signal by filtering only That is, in the ONU transmitter 66, an uplink subcarrier (

) As well as downward signal light (

) Also modulates and transmits the uplink subcarrier (

In order to extract only the data contained in), only the signals of the corresponding band (fu-f _lu <f <fu + f _lu ) are filtered.

)은 상향 신호용 부반송파(

)를 생성하기 위해 광원(

)이 외부 변조기(22)에서 변조된 후 다시 ONU송신기(66)에서 변조된 것이므로, ONU송신기(66)에서 전송하고자 하는 상향 신호를 정확히 복원하기 위해서는 대역통과된 광신호 전류에서 상향 신호용 부반송파 성분(fu)을 제거해야 한다. 이를 위해, 외부 변조기(22)에서 광원(

)을 변조하기 위해 사용된 주파수(fu)의 신호를 발진기(474)로 생성한 후 이 신호를 대역통과된 광신호 전류와 믹싱함으로써 대 역통과된 광신호 전류에서 상향 신호용 부반송파 성분(fu)을 제거하게 된다.The oscillator 474 generates and outputs a signal having a predetermined frequency (fu), and the mixer 475 mixes the optical signal current filtered by the band pass filter (BPF) 473 and the output signal of the oscillator 474 to produce a band. The subcarrier component (fu) for the uplink signal included in the passed optical signal current is removed. That is, the uplink signal includes a value modulated by the ONU transmitter 66 or an optical signal received by the receiver 47 by including an uplink signal.

) Is the subcarrier for the uplink signal (

To generate a light source (

) Is modulated by the ONU transmitter 66 after being modulated by the external modulator 22, so that the subcarrier component for the uplink signal in the bandpass optical signal current (B) is used to accurately restore the upstream signal to be transmitted by the ONU transmitter 66. fu) should be removed. To this end, the light source (in the external modulator 22)

The oscillator 474 generates a signal of the frequency (fu) used to modulate the signal, and then mixes the signal with the bandpass optical signal current to extract the subcarrier component (fu) for the uplink signal from the bandpass optical signal current. Will be removed.

)을 변조하기 위해 사용된 상향 신호전류의 주파수 대역(f＜f_lu)과 동일한 주파수 대역으로 믹싱된 광신호 전류를 필터링함으로써 상향 신호에 대응되는 광신호 전류만 통과시킨다.The low pass filter (LPF) 476 performs low pass (f <f _lu ) filtering on the mixed optical signal current to pass only the optical signal current corresponding to the upstream signal. That is, the low pass filter (LPF) 476 transmits the light (from the ONU transmitter 66).

By filtering the mixed optical signal current in the same frequency band as the frequency band (f <f _lu ) of the uplink signal current used to modulate), only the optical signal current corresponding to the uplink signal passes.

Referring to the operation of the WDM-PON system of the present invention having the above-described configuration as a whole.

)들은 WDM(14)에서 파장 다중화(

)되어 광분기기(16)로 전송된다.Continuous wave laser light generated and output by the laser diodes 12 of the light source providing unit 10 for each subscriber (

) Are used for wavelength multiplexing in the WDM 14.

And transmitted to the optical splitter 16.

)은 광분기기(16)에서 2분기되며 분기된 광(

)은 각각 외부 변조부(20) 및 광분기기(30)로 전송된다.Wavelength multiplexed light (

) Is bi-branched in the optical splitter 16 and diverged

Are transmitted to the external modulator 20 and the optical splitter 30, respectively.

)은 외부 변조기(22)에 의해 fu의 속도로 변조됨으로써 상향 신호용 부반송파(

)로 변화된다. 이러한 변조에 따라, 다중화된 광(

)의 주파수 스펙트럼은 도 3a의 형태에서 도 3b와 같이 변하게 된다. 다음에, 외부 변조기(22)에서 변조된 상향 신호용 부반송파(

)는 복수의 OLT에서 사용될 수 있도록 광분기기(24)에 의해 n개로 분기된 후 대응되는 OLT(40)의 광결합기(44)로 전송된다.Multiplexed light transmitted to the external modulator 20

) Is modulated at the rate of fu by the external modulator 22, so that the uplink subcarrier (

). According to this modulation, multiplexed light (

), The frequency spectrum is changed as shown in FIG. 3B in the form of FIG. 3A. Next, the uplink subcarrier (modulated by the external modulator 22)

) Is branched by the optical splitter 24 to n for use in a plurality of OLTs and then transmitted to the corresponding optical coupler 44 of the corresponding OLT 40.

)은 역시 복수의 OLT에서 사용될 수 있도록 분기되며 분기된 광(

)은 대응되는 OLT(40)로 전송된다.On the other hand, the multiplexed light transmitted to the optical splitter 30 (

) Can also be used in multiple OLT branches and branched light (

) Is sent to the corresponding OLT 40.

)은 광서큘레이터(41)에 의해 WDM(42)으로 전송되어 파장별로 분리된다.Light branched from the optical splitter 30

) Is transmitted to the WDM 42 by the optical circulator 41 and separated by wavelength.

)은 도 5에서와 같이 반도체 광증폭기(R-SOA)인 OLT송신기(43)에서 하향 신호전류에 따라 하향 신호광(

)으로 변조된 후 송신된다. 즉, OLT(40)에서 각 가입자측으로 전송하고자 하는 데이터가 각 가입자에 할당된 광(

)에 실려 송신된다.Wavelength-separated light (

As shown in FIG. 5, the downlink signal light according to the downlink signal current in the OLT transmitter 43 which is a semiconductor optical amplifier (R-SOA)

Is modulated by) and transmitted. That is, the data to be transmitted from the OLT 40 to each subscriber is assigned to each subscriber.

Is sent on).

)은 WDM(42)에서 파장 다중화된 후 광서큘레이터(41)에 의해 광결합기(44)로 전송된다.Downlink signal light transmitted from the OLT transmitter 43 (

Is wavelength multiplexed in the WDM 42 and then transmitted by the optical circulator 41 to the optical coupler 44.

)와 파장 다중화된 하향 신호광(

)은 광결합기(44)에서 결합(

)된 후 광서큘레이터(45)에 의해 WDM 필터(50)로 전송된다.Subcarrier for uplink signal modulated by external modulator 20 (

) And wavelength multiplexed downlink signal light (

) Is combined in the optical coupler 44

And then transmitted by the optical circulator 45 to the WDM filter 50.

)은 WDM 필터(50)에서 각 가입자별로 파장 분리된 후 해당 가입자의 ONU(60)로 전송된다.Combined light (

) Is wavelength-separated for each subscriber in the WDM filter 50 and then transmitted to the ONU 60 of the subscriber.

)은 광분기기(62)에서 2분기되어 각각 ONU수신기(64) 및 ONU송신기(66)로 동시에 전송된다.Wavelength-separated light transmitted to the ONU 60 (

) Is bifurcated at the optical splitter 62 and simultaneously transmitted to the ONU receiver 64 and the ONU transmitter 66, respectively.

)이 광검출기(642)에 의해 전기신호인 광신호 전류로 변환된 후 증폭기(644)에서 증폭된다. 증폭된 광신호 전류는 투과 대역폭이 f＜f_ld인 저역통과필터(646)를 거치면서 상향 신호용 부반송파(

)에 대응되는 광신호 전류 성분은 제거되고 하향 신호광(

)에 대응되는 광신호 전류 성분만 남게 되며 이를 이용하여 하향 신호를 복원하게 된다.In the ONU receiver 64, as shown in FIG.

) Is converted into an optical signal current which is an electrical signal by the photodetector 642 and then amplified in the amplifier 644. The amplified optical signal current passes through a low pass filter 646 having a transmission bandwidth of f <f _ld and an uplink subcarrier (

), The optical signal current component corresponding to the

Only the optical signal current component corresponding to) remains, and the downlink signal is restored using this.

) 뿐만 아니라 하향 신호광(

)이 모두 활성층 도파로(662)로 입사되어 상향 신호전류에 따라 변조된다. 변조된 광(

)은 다시 광분기기(62)를 거쳐 WDM 필터(50)로 전송되어 다른 ONU로부터의 신호광들과 함께 파장 다중화된다. 이때, ONU(60)와 WDM 필터(50)는 도 2에서와 같이 동일한 하나의 광선로만을 이용하여 하향 광 및 상향 광을 전송하게 된다.On the other hand, in the ONU transmitter 66, as shown in FIG.

) As well as downward signal light (

Are all incident on the active layer waveguide 662 and modulated according to the upward signal current. Modulated light (

) Is again sent through the optical splitter 62 to the WDM filter 50 to be wavelength multiplexed with signal lights from another ONU. At this time, the ONU 60 and the WDM filter 50 transmit the downlink light and the uplink light using only one same optical path as shown in FIG. 2.

)은 광서큘레이터(40)에 의해 WDM(46)으로 전송되어 파장 분리된 후 대응되는 OLT수신기(47)로 전송된다.Wavelength multiplexed light (

) Is transmitted to the WDM 46 by the optical circulator 40 and the wavelength is separated and then transmitted to the corresponding OLT receiver 47.

)이 광검출 기(471)에 의해 전기신호인 광신호 전류로 변환된 후 증폭기(472)에 의해 증폭된다. 증폭된 광신호 전류는 투과 대역폭이 fu-f_lu＜f＜fu+f_lu 인 대역통과필터(473)을 거치면서 변조된 하향 신호광(

)에 대응되는 광신호 전류 성분은 제거되고 변조된 상향 신호용 부반송파(

)에 대응되는 광신호 전류 성분만 남게 된다.In the OLT receiver 47, as shown in FIG.

) Is converted into an optical signal current which is an electrical signal by the photodetector 471 and then amplified by the amplifier 472. The amplified optical signal is transmitted through the current bandwidth is _{fu-f lu <f <fu} + f lu which goes through the band-pass filter 473. The modulated downlink signal (

The optical signal current component corresponding to the subcarrier for the uplink signal is removed and modulated.

Only the optical signal current component corresponding to) remains.

)는 하향 신호광과 같이 소스광(

)이 송신기(66)에 의해서만 변조된 것이 아니라 서브 캐리어로 사용되기 위해 외부 변조기(22)에 의해서도 변조된 것이므로 상향 신호를 복원하기 위해서는 외부 변조기(22)에 의해 변조된 것을 다시 복조해줘야 한다. 따라서, 하향 신호에 대한 ONU수신기(64)와는 달리 상향 신호에 대한 수신기(47)에서는 대역통과된 광신호 전류에 주파수(fu) 즉 외부 변조기(22)에서 소스광(

)을 변조하기 위해 사용된 주파수(fu)를 믹싱시켜 해당 주파수 성분을 제거한다. 주파수(fu) 성분이 제거된 광신호 전류는 투과 대역폭이 f＜f_lu 인 저역통과필터(476)를 거치면서 하향 신호에 대응되는 광신호 전류만이 남게 되며 이를 이용하여 하향 신호를 복원하게 된다.However, at this time, an uplink subcarrier used as a carrier for transmitting an uplink signal (

) Is the source light (

) Is not only modulated by the transmitter 66 but also by the external modulator 22 to be used as a subcarrier, so that the modulated by the external modulator 22 must be demodulated again to recover the uplink signal. Therefore, unlike the ONU receiver 64 for the downlink signal, in the receiver 47 for the uplink signal, the frequency (fu) is applied to the bandpassed optical signal current, that is, the source light (in the external modulator 22).

We mix the frequencies (fu) used to modulate this to remove that frequency component. The optical signal current from which the frequency (fu) component is removed passes through the low pass filter 476 having a transmission bandwidth of f <f _lu , leaving only the optical signal current corresponding to the downlink signal, thereby restoring the downlink signal. .

As described above, the WDM-PON system of the present invention enables a more flexible network structure by enabling up / down signal transmission through a single channel through the above-described configuration and method.

Claims (20)

An external modulator for modulating a wavelength division multiplexed light source to generate a subcarrier for an uplink signal; Modulating the light source to generate a downlink signal light, combining the generated downlink signal light with an uplink subcarrier generated by the external modulator to transmit the downlink light as a downlink light, and to restore the uplink signal from the uplink light received through the light path; OLT; An ONU receiving the wavelength-separated downlink light and restoring a downlink signal from the downlink signal light among the downlink light, modulating the downlink light, and transmitting the downlink light as the uplink light; And Upward and downward signals using a single channel having a WDM filter for wavelength-dividing the downlink light from the OLT to a corresponding ONU and wavelength-division multiplexing the upstream light from the ONUs to the OLT. WDM-PON system that enables the transmission of data. The method of claim 1, wherein the OLT An OLT transmitter for wavelength-separating the light source to modulate the downlink signal light for each wavelength and to perform wavelength division multiplexing on the modulated downlink signal light; An optical coupler for coupling the uplink subcarrier from the external modulator and the downlink signal light from the OLT transmitter; An OLT receiver for wavelength-separating the upward light from the WDM filter and restoring the upward signal for each wavelength; And And an optical circulator for transmitting the downward light from the optical coupler to the WDM filter and the upward light from the WDM filter to the OLT receiver. WDM-PON system to enable transmission. The method of claim 2, wherein the ONU is An optical splitter for splitting and outputting the downward light from the WDM filter; An ONU receiver for recovering a downlink signal from the first branch downlink light branched from the optical splitter; And WDM for transmitting up and down signals using a single channel characterized in that it comprises an ONU transmitter for modulating according to the uplink signal current to the second branch downward light branched from the optical splitter. -PON system. 4. The receiver of claim 3, wherein the ONU receiver is A first photodetector for converting the downward light into an optical signal current; And A first low pass filter for filtering the optical signal current to pass the optical signal current corresponding to the downlink signal light; and enabling a WDM-PON system to transmit up / down signals using a single channel. . The method of claim 4, wherein the OLT transmitter An OLT transmitter for modulating and transmitting the input light into the downlink signal light according to the downlink signal current; And And separating the light source into the OLT transmitter and transmitting the downlink signal light from the OLT transmitter to the optical coupler by performing wavelength division multiplexing on the downlink signal. WDM-PON system that enables the transmission of data. 6. The filter of claim 5, wherein the first low pass filter WDM-PON system that enables the transmission of the up and down signals using a single channel, characterized in that the transmission bandwidth is smaller than the frequency of the downlink signal current. The method of claim 3, wherein the OLT receiving unit An OLT receiver for restoring the upstream signal from upstream light for each wavelength input; And And a second WDM for wavelength-separating the upstream light from the optical circulator and transmitting the wavelength to the OLT receiver. The method of claim 7, wherein the OLT receiver A second photodetector for converting the input upward light into an optical signal current; A band pass filter for filtering the optical signal current to pass the optical signal current corresponding to the uplink subcarrier; An oscillator for generating a signal having the same frequency as the modulation frequency of the external modulator; A mixer for mixing the output signal of the oscillator and the output current of the bandpass filter to remove the uplink subcarrier component from the bandpass optical signal current; And And a second low pass filter for filtering the output signal of the mixer to pass the optical signal current corresponding to the upstream signal. The WDM-PON enables transmission of the upstream and downstream signals using a single channel. system. 9. The filter of claim 8, wherein the second low pass filter WDM-PON system that enables the transmission of the up and down signals using a single channel, characterized in that the transmission bandwidth is smaller than the frequency of the uplink signal current. The method of claim 1, wherein the external modulator WDM-PON system for enabling the transmission of the up and down signals using a single channel, characterized in that for generating a sub-carrier for the uplink signal by modulating the light source to a frequency greater than the bandwidth of the downlink signal. The method of claim 1, And a second optical splitter which splits the light source into a plurality of lights so that the light source can be shared by a plurality of OLTs. The WDM-PON system enables transmission of up and down signals using a single channel. The method of claim 11, wherein the external modulator WDM-PON to enable the transmission of the up and down signals using a single channel, characterized in that it further comprises a third optical splitter for splitting the uplink sub-carrier for a plurality of OLT to share a plurality of light system. Modulating a light source having the same wavelength into an uplink subcarrier and a downlink signal light, respectively, and then modulating the uplink subcarrier and the downlink signal light to transmit the downlink light as a downlink light, and to restore an upstream signal from the uplink light received through the lightpath. Telephone station apparatus; A subscriber device for restoring a downlink signal from the downlink signal light among the downlink light, and modulating the downlink light and transmitting the downlink light as an uplink light; And Uplink and downlink using a single channel having a remote node that transmits the downlink light from the telephone station apparatus to the subscriber station by wavelength separation and transmits the uplink light from the subscriber apparatus by wavelength division multiplexing to the telephone station apparatus. WDM-PON system that allows the transmission of signals. The apparatus of claim 13, wherein the telephone station apparatus An external modulator for generating the uplink subcarrier by modulating the light source at a first frequency; An OLT transmitter for modulating the light source with a downlink signal current to generate the downlink signal light; An optical coupler for coupling the uplink subcarrier and the downlink signal light; And And an OLT receiver configured to recover the uplink signal from the uplink subcarrier modulated by the subscriber device among the uplink signals. 14. The subscriber device of claim 13, wherein the subscriber device is An optical splitter for splitting the downward light; An ONU receiver which converts a first branched light among the branched downlights into an optical signal current to filter an optical signal current corresponding to the downlink signaled light and then restores the downlink signal from the filtered signal; And WDM-PON to enable the transmission of the up and down signals using a single channel, characterized in that it comprises an ONU transmitter for modulating the second branched light of the branched downward light into an uplink signal current to transmit to the optical splitter. system. In the WDM-PON method of supplying a light source from the telephone station apparatus to each subscriber apparatus, A first step of dividing the light source by the telephone station apparatus to modulate a first branched light into an uplink subcarrier and a second branched light into a downlink signal light; A second step of combining, by the telephone station apparatus, the modulated uplink subcarrier and the downlink signal light and transmitting the downlink light to the subscriber device; A third step of the subscriber apparatus recovering a downlink signal using the downlink signal light of the downlink light, modulating the downlink light, and transmitting the downlink light to the telephone station apparatus as an uplink light; And And a fourth step of recovering an uplink signal by using the uplink subcarrier of the uplink light in the telephone station apparatus. The method of claim 16, wherein the uplink subcarrier The uplink and downlink signal transmission method using a single channel, characterized in that the modulation is a frequency larger than the bandwidth of the downlink signal. The method of claim 16, wherein the third step is The first branched light is converted into an electric signal by dividing the downward light, and then the electrical signal corresponding to the downward signal light is filtered from the converted electric signal to restore the downward signal. And modulating and transmitting the signal to the telephone station apparatus. 19. The method of claim 18, wherein the fourth step is Converting the uplink light into an electrical signal and then filtering the electrical signal corresponding to the uplink subcarrier from the converted electrical signal and removing the uplink subcarrier component from the filtered electrical signal to restore the uplink signal Up and down signal transmission method using a single channel. 20. The method of claim 19, wherein the fourth step is A phase using a single channel to remove the uplink subcarrier component from the filtered electrical signal by mixing a signal having the same frequency as the modulation frequency used to generate the uplink subcarrier to the filtered electrical signal. Downward signal transmission method.

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