KR20080085994A - Adjacent crosstalk-free bidirectional wavelength division multiplexing passive optical network - Google Patents

Abstract

A bidirectional WDM(Wavelength Division Multiplexing)-PON(Passive Optical Network) is provided to remove inter-channel crosstalk effectively and to expand the number of channels twice as compared to an existing WDM-PON by using 4 BLSs(Broadband Light Sources) having their respective wavelength bands. An OLT(Optical Line Terminal) in a WDM-PON comprises 4 BLSs(170,180,220,230), a BIM(Band Interleave Multiplexer/demultiplexer)(160), and transceivers(110-130). The BLSs have their respective wavelength bands. The BIM classifies and outputs the injection light created by two of the BLSs and the Tx signals created by the injection light of the other BLSs according to odd channels and even channels. In this case, the injection light or Tx signal of each band has a different channel from a neighbor band. Each transceiver creates Tx signals with the injection light outputted from the BIM, filters the Tx signals outputted from the BIM, and receives Tx signals of preset channel-by-channel bands only.

Description

Adjacent crosstalk-free bidirectional wavelength division multiplexing passive optical network

1 is a block diagram illustrating a wavelength division multiplexing passive optical network (WDM-PON) using a light source whose wavelength is locked to a non-coherent light source according to the prior art.

2 is a diagram illustrating a WDM-PON according to an embodiment of the present invention.

3 is a diagram illustrating wavelength allocation of an uplink signal and a downlink signal in a WDM-PON according to an embodiment of the present invention.

4 is a block diagram illustrating a band cross separator included in a WDM-PON according to an embodiment of the present invention.

The present invention relates to a wavelength-division-multiplexing passive optical network (WDM-PON). More specifically, the present invention provides a wavelength division multiplexer and WDM filter in a wavelength division multiplexing passive optical network using a light source that is wavelength locked to a spectrum-incoherent light. The present invention relates to a subscriber network system configured to prevent crosstalk between adjacent channels using a band interleave multiplexer / demultiplexer (BIM).

Recently, with the spread of the Internet, various data services and multimedia services have rapidly increased, thereby increasing the speed of subscriber networks and increasing transmission capacity. As one of the solutions, a passive optical network of wavelength division multiplexing with excellent scalability and security has been attracting attention. The wavelength division multiplexing scheme refers to a method of multiplexing and transmitting multiple optical signals using one optical fiber while giving a unique wavelength to each subscriber to provide subscribers with signals having different wavelengths.

In the wavelength division multiplexing subscriber network, signals of multiple wavelengths are multiplexed and transmitted, so that the two multiplexers / demultiplexers located at a central office (CO) and a local node (RN) are used. It is necessary to match the channel wavelengths and to match a plurality of light source wavelengths to each channel wavelength of the multiplexer. Currently, a method of using a distributed feedback laser (DFB laser) used in a backbone network as a light source is utilized, but this is not economical because it uses an expensive DFB laser.

Therefore, various methods using spectral segmentation have been proposed, and the spectral segmentation of non-coherent light is injected into a fabric-perot laser or a reflective semiconductor optical amplifier (RSOA). In this regard, a method of immersing a wavelength in automatically injected light has been proposed, and a lot of research is being conducted, and it is actually used in the field. This method does not require wavelength alignment between the light source and the multiplexer / demultiplexer, so the maintenance is simple and economical network operation is possible. However, since the multiplexer / demultiplexer uses spectral-divided light, the line width of the light source is relatively wide, which causes adjacent channel crosses due to incomplete alignment of the channel wavelengths of the multiplexer / demultiplexer located at the central base station and the local node. The impact of flick has a big disadvantage.

The present invention provides a wavelength division multiplexing passive optical network in which crosstalk of adjacent channels does not occur by using a band cross separator configured using a wavelength shifter and a plurality of WDM filters. It aims to provide.

A wavelength division multiplexing passive optical network according to an embodiment of the present invention uses transmission light output from 2n broadband light sources (BLSs), band cross separators, and band cross separators having different wavelength bands. It generates a signal, and includes a transmitting and receiving device for separating and receiving only a predetermined band for each channel of the transmission signal output from the band cross separator. The band cross-separator divides the injection light and the transmission signal generated by the broadband light source into odd and even channels according to the wavelength, and outputs the channel in which the injection light or transmission signal of each band is different from the adjacent band. It characterized in that the output to have.

Hereinafter, with reference to the accompanying drawings will be described the configuration of the present invention. In this specification, descriptions of well-known functions or configurations are omitted for clarity of the gist of the present invention.

1 is a block diagram showing a bidirectional WDM-PON using a light source wavelength-locked to a non-coherent light source according to the prior art. A-band broadband light sources and B-band broadband light sources are integer multiples of the free spectral range (FSR) of an arrayed waveguide grating (AWG) located at the central base station and regional nodes. Two-way communication is possible by using transmission line of. An implementation method thereof is described in detail in Korean Patent Publication No. 10-2004-0103085, and detailed description thereof will be omitted.

2 is a diagram illustrating a WDM-PON network without crosstalk between adjacent channels according to an embodiment of the present invention. Two non-coherent broadband light sources 170, 180, 220, 230 are shown in FIG. 2, each of which is an integer multiple of the FSR of the AWGs 140, 150, 270, 270 used at the central base station and local nodes. have. The A and B bands are injected into a transmitter (Tx: transmitter) 121 located at the central base station via the broadband light source combiner 200 and used as a downlink light source, and the C and D bands are passed through the broadband light source combiner 200. The light is injected into the transmitters 282 and 292 located in the optical subscriber devices 280 and 290 after passing through the optical path 240 and used as a light source for uplink transmission. The transmitter for receiving the injected light and outputting a light source for transmission may include a Fabry Perot laser or RSOA.

First, a process of injecting the broadband light sources 220 and 230 of the A and B bands into the transmitter 121 of the central base station in order to be used as the downlink light source will be described. The injection light of the A-band broadband light source 220 and the B-band broadband light source 230 is combined in the WDM coupler 210 and then transmitted to the band cross-separator BIM1 160 via the broadband light source combiner 200. At this time, the band cross separator 160 outputs through two output ports. As shown in FIG. 4, the band cross separator 160 outputs odd channels in the A and C bands and even channels in the B and D bands to the first port 6, and A and A to the second port 7. It is a device made by combining wavelength shifter 5 and eight WDM filters 10, 20, 30, 40, 50, 60, 70, 80 to output even channels in C band and odd channels in B and D band. . At this time, the wavelength of each channel of the band cross separator 160 is set to be the same as the AWG (140, 150, 260, 270) located in the central base station and the local node.

The injection light output to the first port of the band cross separator, that is, the injection light of the odd channel of the A band and the even channel of the B band, is divided into channels according to the wavelength at the AWG1 140 to a transmitter connected to the AWG1 140. Is entered. The AWG1 140 and AWG2 150 are grids having an array of 1 × N, so that the channels of optical signals passing through the grids can be separated. Thus, the first port outputs a downlink transmission signal whose wavelength is alternately locked to the odd channel wavelength in the A band and the even channel wavelength in the B band.

On the other hand, the injection light output to the second port 7 of the band cross separator, that is, the injection light of the even channel of the A band and the odd channel of the B band, is divided into channels according to the wavelength at the AWG2 150 and thus the AWG2 150. Is input to the transmitter connected to. Thus, the downlink transmission signal is alternately locked to the odd channel wavelength in the B band and the even channel wavelength in the A band.

The above-described downlinked light source is multiplexed as a downlink signal in the AWG1 140 and AWG2 150, respectively, and the downlinked downlink signal is input to the first port and the second port of the band cross separator BIM1 160. do. The downlink signal finally combined in the BIM1 160 is combined with the injection light of the broadband incoherent light sources 170 and 180 of the C and D bands in the broadband light coupler 200 and passes through the trunk line 240 to the second signal. A band cross separator 250 is reached. At this time, the light reaching the second band cross separator 250 is mixed with the downlink transmission signal of the A and B bands and the injection light of the broadband light sources of the C and D bands to be injected into the upward light source.

The second bandpass separator BIM2 250 has two output ports, a first port and a second port, similarly to the first bandcross separator BIM1 160. First, the first port outputs a downlink transmission signal of an odd channel of the A band and an even channel of the B band. At this time, as shown in FIG. 4, the odd-channel incoherent light source in the C band and the even-channel incoherent light source in the D band are also output. The second port outputs downlink transmission signals of odd-numbered channels in the B band and even-numbered channels in the A-band, and incoherent light injection light of odd-numbered channels in the D-band and even channels in the C band.

The light output to the first port of the second band cross separator 250 is demultiplexed for each wavelength in the connected AWG3 260 and then passes through each distribution optical fiber to the optical network unit (ONU) 280. Is entered. The AWG3 260 and AWG4 270 are gratings with an array of 1 x N to separate the channels of the optical signal passing through the grating. In this case, the light transmitted to the optical subscriber device connected to the odd channel of the AWG3 260 is a downlink signal of the A band and the incoherent light source injection light of the C band, and the optical subscriber device connected to the even channel. The downlink signal of the B band and the non-coherent light source injection light of the D band are transmitted.

The downlink signal arriving at the optical subscriber device 280 and the injected light are separated by the WDM filter 281. The injected light is input to the transmitter 282 to fix the wavelength of the transmitter. In this case, the transmitter may include a Fabry-Perot laser or RSOA. Meanwhile, the downlink signal separated by the WDM filter 281 arrives at a receiver (Rx) 283 through an A band or B band transmission filter. In this case, the band pass filter 284 located in front of the receiver has an A band transmission characteristic in a subscriber device connected to an odd channel of the AWG3 260 and a B band transmission characteristic in a subscriber device connected with an even channel. That is, the downlink transmission signal of different bands is output from the adjacent ports of the AWG3 260, and since there is a filter that transmits only the signal band required at the front end of the receiver, the crosstalk of the adjacent channel is automatically blocked.

Similarly, the light output to the second port of the second band cross separator is demultiplexed by wavelength in the connected AWG4 270 and then input to the optical subscriber device 290 through each of the distribution optical fibers. In this case, the light transmitted to the optical subscriber device connected to the odd channel of the AWG4 270 is a downlink signal of the B band and an incoherent light source injection light of the D band, and the optical subscriber device connected to the even channel. The downlink signal of the A band and the incoherent light source injection light of the C band are transmitted.

The downlink signal and the injected light arriving at the optical subscriber device 290 are separated by the WDM filter 291. The injected light is input to the transmitter 292 to fix the wavelength of the transmitter. In this case, the transmitter includes a Fabry Perot laser or RSOA. Meanwhile, the downlink signal separated by the WDM filter 291 reaches the receiver 293 through the A band or B band transmission filter. In this case, the band pass filter 294 located at the front of the receiver has a B band transmission characteristic at a subscriber device connected to an odd channel of the AWG4 270 and an A band transmission characteristic at a subscriber device connected to an even channel. That is, downlink signals of different bands are output to the adjacent ports of the AWG4 270, and a filter that transmits only the required signal bands at the front of the receiver automatically blocks the crosstalk of the adjacent channels.

In addition, upstream light sources are alternately locked to wavelengths of different bands with respect to adjacent channels, and are transmitted upward in the same manner, and then filtered by band-pass filters in front of each receiver to block crosstalk of adjacent channels. As described above, broadband light sources of different bands are injected to adjacent channels to alternately set the wavelengths of transmission light sources to different bands, and place a bandpass filter in front of the receiver so that the AWGs located in the central base station and the local node are located. The crosstalk of adjacent channels due to wavelength mismatch between them can be effectively eliminated.

3 is a diagram illustrating wavelength allocation of an uplink signal and a downlink signal in a WDM-PON without adjacent channel crosstalk according to an exemplary embodiment of the present invention. As shown, it can be seen that the broadband light sources in the A and B bands are separated by the FSR of the AWG and used as the downward light sources, and the broadband light sources in the C and D bands are similarly separated by the FSR of the AWG and used as the upward light sources. . Meanwhile, it can be seen that the broadband light sources of the B band and the C band are separated by an integer multiple of the FSR. And AWG1 and AWG3 are allocated A band, C band odd channel and B band, D band even channel for communication, and AWG2 and AWG4 are allocated A band, C band even channel and B band, and D band odd channel. Communicate.

4 is a detailed block diagram illustrating a band cross separator configured by specially combining a wavelength shifter and a WDM filter in order to configure a WDM-PON having no adjacent channel crosstalk according to an exemplary embodiment of the present invention.

Looking at the operating principle that crosses by band, the light source inputted to the wavelength alternator (5) by combining the A, B, C and D bands, first to the odd and even channels according to each wavelength in the wavelength alternator (5) Are separated. The wavelength shifter 5 has a first port and a second port, and a separate odd channel signal is output to the first port, and a separate even channel signal is output to the second port.

The odd channel signal outputted to the first port transmits only the C band in the first WDM filter 10 and reflects and separates the remaining bands. The reflected signals of the A, B, and D bands are separated into the A, B, and D bands again by the third WDM filter 30, so that the signals of the A band are input to the fourth WDM filter 40 and the B, D bands. The signal is input to the eighth WDM filter 80. On the other hand, after the even channel signal output to the second port is separated into the C band and the remaining band in the fifth WDM filter 50, the reflected signal of the A, B, D band is A again in the seventh WDM filter 70 It is divided into band and B, D band. The even-channel signal of the A band is input to the eighth WDM filter 80 and combined with the signals of the odd channel of the B and D bands to the sixth WDM filter 60.

In the sixth WDM filter 60, the even channel in the A band, the odd channel in the B and D bands output from the eighth WDM filter 80, and the even channel in the C band output from the fifth WDM filter 50 are included. The signals are combined and output to the second port 7. Meanwhile, even-channel signals in the B and D bands separated from the seventh WDM filter 70 are input to the fourth WDM filter 40, are combined with light of odd-channels in the A band, and input to the second WDM filter 20. . In the second WDM filter 20, the light of the odd channel of the C band and the light of the odd channel of the B and D band and the odd channel of the A band are combined to output the first port (6). Will be printed).

On the other hand, when the optical signal is input through the first port 6 and the second port 7 in the reverse direction to the above-described process, the optical signal proceeded in the reverse direction is finally combined in the wavelength shift. At this time, the first WDM filter, the fifth WDM filter, the second WDM filter, the sixth WDM filter, the third WDM filter, the seventh WDM filter, the fourth WDM filter, and the eighth WDM filter have the same characteristics.

By constructing a wavelength division multiplexing passive optical network including a band cross separator configured according to the above-described configuration, a crosstalk between adjacent channels that may occur due to inconsistency of AWG transmission wavelengths located at a central base station and a local node in a WDM-PON Can be removed. This has the advantage that the odd and even channels can be arranged to belong to different spectral bands using fewer band cross separators compared to the prior art. In addition, in the configuration according to the present invention, since the waveguide grating of 1 x N array is used unlike the prior art, the implementation is simple and economical.

While specific embodiments of the present invention have been illustrated and described, the technical spirit of the present invention is not limited to the accompanying drawings and the above description, and various modifications can be made without departing from the spirit of the present invention. It will be apparent to those skilled in the art, and variations of this form will be regarded as belonging to the claims of the present invention without departing from the spirit of the present invention.

The present invention provides a WDM-PON wavelength division multiplexing subscriber network that can effectively eliminate the adjacent channel crosstalk problem caused by the wavelength mismatch of the multiplexer / demultiplexer located in the central base station and the local node. In addition, according to an embodiment of the present invention by configuring a system using four different bands of non-coherent broadband light source, the number of channels that can be accommodated in one system can be doubled compared to the existing WDM-PON. This is easy and economical to implement because it uses only two band cross separators and uses a simpler array of waveguide gratings.

Claims (12)

2n broadband light sources having different wavelength bands; The injection signal generated by the n broadband light sources and the transmission signals generated by the injection light of the remaining n broadband light sources are divided into an odd channel and an even channel according to a wavelength, and are outputted together with the injection of each band output. A band cross separator for outputting an optical signal or the transmission signal to have a channel different from an adjacent band; And a transmission and reception device generating a transmission signal using the injected light output from the band cross separator, and separating and receiving only a predetermined band for each channel among the transmission signals output from the band cross separator. Wavelength division multiplex passive optical network. The method of claim 1, The band cross separator, A wavelength shifter for dividing the injected light and the transmission signal into an even channel and an odd channel according to a wavelength; And The injection light and the transmission signal output from the wavelength shifter are separated according to a band, and each of the separated outputs has odd channel injection light, even channel injection light, odd channel transmission signal, and even channel having different bands from each other. A wavelength division multiplex passive optical network comprising a plurality of WDM filters configured to contain a signal for transmission. The method of claim 1, The transceiver device, A WDM filter for separating and transmitting the injected light and the transmission signal output from the band cross separator; A transmitter for receiving the injected light from the WDM filter and generating a signal for transmission; A band pass filter which receives the transmission signal from the WDM filter and passes only the transmission signal of one band preset for each channel; And And a receiver for receiving the transmission signal passing through the band pass filter. The method according to claim 1 or 3, N is 2, the wavelength division multiplex passive optical network. The method according to claim 1 or 3, And said respective broadband light sources are separated by a free spectral spacing. The method according to claim 1 or 3, The broadband light source is an amplified spontaneous emission (ASE) light source using an erbium doped fiber (EDF), wavelength division multiplex passive optical network. The method according to claim 1 or 3, The broadband light source is a wavelength division multiplex passive optical network, characterized in that the light source using a Raman amplifier. The method according to claim 1 or 3, The broadband light source is a wavelength division multiplex passive optical network, characterized in that the light source using a semiconductor amplifier. The method according to claim 1 or 3, The optical signal band of the broadband light source is wavelength division multiplexing passive type, characterized in that one of the E-band (extended band), S-band (short band), C-band (conventional band) or L-band (long band) Optical network. A wavelength shifter for dividing the injection light and the transmission signal of different bands into odd and even channels according to the wavelength; Two first type WDM filters connected to the odd channel output and the even channel output of the wavelength shifter, respectively, passing only one band and reflecting the remaining band; Two second type WDM filters respectively connected to the first type WDM filters, passing only one of the reflected bands and reflecting the remaining bands; Two third type WDM filters respectively connected to the second type WDM filters to pass only one of the reflected bands and reflect the remaining bands; A channel of each band by outputting the injection light and the transmission signal of a band passed from the WDM filters connected to one of an even channel and an odd channel, and a band reflected from the WDM filters connected to the other channel; A band cross separator comprising two fourth type WDM filters which cross each other to separate them. A plurality of injection light and transmission signals having different bands are output to be divided into odd and even channels according to the wavelength, but the injection light and the transmission signal of each band output together have a different channel from the adjacent band Outputting; Separating only a predetermined band among the output signals for transmission; And receiving the injected light and the transmission signal in the separated band in the separating step. Outputting a plurality of injected light and transmission signals having different bands into odd and even channels according to wavelengths; Passing only the output corresponding to one band and reflecting the output of the remaining band from the separated odd channel output and the even channel output; The process of passing only the output of another band of the reflected outputs and reflecting the outputs of the remaining bands, and passing only the output of one of the outputs of the reflected bands and reflecting the outputs of the remaining bands until all bands are separated. Repeating; And Band crossing, characterized in that the channels of each band are separated by crossing the bands passed from one of the odd channel output and the even channel output, and the combined light and the transmission signal of the bands reflected from the remaining channels. Separation method.

Images