KR100784115B1 - Passive optical network system using remote pumping optical amplifier - Google Patents

Abstract

In the present invention, by using a remote pumping optical amplifier to increase the transmission distance of the passive optical subscriber network system, it is possible to amplify the optical signal without using power in the Remote Node (RN), which enables long-distance transmission, The present invention relates to a passive optical subscriber network system using a remote pumping optical amplifier that enables convenient and economical configuration of a long-range passive optical subscriber network system. The present invention is a passive optical subscriber network system in which an optical line terminator (OLT) and a remote node are connected by optical fibers, wherein the OLT stage includes a pumping light source for pumping an erbium-doped fiber (EDF). And, the RN end is characterized in that it is provided with an EDF. The remote pumping optical amplifier is a bidirectional remote pumping optical amplifier for simultaneously amplifying an uplink optical signal and a downlink optical signal, or a bidirectional remote pumping optical amplifier for simultaneously amplifying a C-band downlink optical signal and an L-band uplink optical signal, or L- The bidirectional remote pumping optical amplifier for amplifying the band downlink optical signal and the C-band uplink optical signal at the same time, or the one-way remote pumping optical amplifier for selectively amplifying only the uplink optical signal or the downlink optical signal.

Passive optical subscriber network system, transmission distance increase, transmission capacity increase, remote pumping optical amplifier, up and down optical signal, EDF

Description

Passive optical network system using remote pumping optical amplifier

1 is a block diagram showing the configuration of a conventional general passive optical network (PON).

2 is a graph showing an example in which the intensity of light output by the Stimulated Brillouin Scattering (SBS) phenomenon does not increase even when the intensity of light incident on the optical fiber is increased.

Figure 3 is a block diagram showing a preferred embodiment of a passive optical subscriber network system using a remote pumping optical amplifier according to the present invention.

Figure 4 is a block diagram showing the structure of a passive optical subscriber network system using a remote pumping optical amplifier according to a first embodiment of the present invention.

FIG. 5 is a graph showing a change in intensity of a downlink optical signal according to an expected distance in a passive optical subscriber network system using a remote pumping optical amplifier of the present invention and a passive optical subscriber network system.

6 shows a remote pumping optical amplifier when the wavelength band of the downlink optical signal of the present invention is C-band (1530 nm ~ 1565 nm) and the wavelength band of the uplink optical signal is L-band (1570 nm ~ 1605 nm). A block diagram showing a second embodiment of the invention for the following.

7 is a block diagram showing a structure using an optical circulator according to a second embodiment of the present invention;

8 is a block diagram showing the structure of a passive optical subscriber network system using a remote pumping optical amplifier in the case where the up-down signal of the present invention uses different optical fibers.

9 is a block diagram showing the structure of a remote pumping optical amplifier using the optical fiber grating of the present invention.

<Description of the symbols for the main parts of the drawings>

20: optical transmitter

21, 31, 41, 51, 66, 70: pump light source (Pump LD)

22, 33, 44, 54, 62, 68, 72: EDF

23: optical receiver

30, 40, 50, 60: OLT

32, 42, 52, 61, 67, 71: WDM Coupler

34, 46, 56, 64: RN

35, 47, 57, 65: ONU

43, 45: C / L-band WDM Coupler

53, 55, 63: Optical circulator

69: optical path for upward optical signal

73: fiber optic grating

The present invention relates to a passive optical network (PON), and more particularly, to amplify a signal using EDFA using a remote pump light source at a remote node of an existing PON system. The present invention relates to a passive optical subscriber network system using a remote pumping optical amplifier for increasing capacity and transmission distance.

In the conventional access network of a subscriber system, a simple voice level service using a copper wire between a switch and a terminal for narrow band service is mainly used for low speed data. Recently, however, subscriber demand for various types of broadband services such as VOD, CATV, and HDTV has increased, and Internet services have exploded, and multimedia traffic will soon surpass voice traffic. In order to smoothly provide such broadband service and Internet demand to subscribers, the construction of optical subscriber network is very essential.

1 is a block diagram showing the configuration of such a conventional general PON.

As shown, the conventional PON system is composed of an optical line terminator (OLT) 10, a remote node 11, an optical network unit 12 (ONU). The structure and role of each stage will be briefly described. In the OLT stage 10, the downlink optical signal is transmitted to the RN stage 11, and the RN stage 11 receives the downlink optical signal transmitted from the OLT stage 10. Transmission is performed to each ONU stage 12 using a divider or a wavelength divider.

Similarly, the uplink optical signals generated at each ONU stage 12 are multiplexed at the RN stage 11 and then transmitted to the OLT stage 10. The optical element configuring the RN stage 11 uses an optical intensity divider or a wavelength divider according to the type of the PON system.

Such a conventional PON system is mainly designed to connect the telephone station and the subscriber in the downtown section so that the distance between the OLT stage 10 and the ONU stage 12 does not exceed 20 km. However, if the distance between the telephone company and the subscriber is long, such as in the suburbs or the islands, the transmission distance may increase to more than 20 km.

Therefore, when the transmission distance increases, an optical amplifier that inevitably compensates for the loss of the optical signal must be used, but in the PON system, since the RN stage 11 does not use power, the optical amplifier operates in the RN stage 11. There is a problem that cannot be done.

If the optical amplifier is used, since the power is used at the RN stage 11 for this purpose, not only the power cost but also the cost of installing the power and maintaining the power stably, and also requiring space for the power installation There was a problem.

In addition, without using an optical amplifier, it is also possible to increase the intensity of the optical signal transmitted from the OLT stage 10, in which case the specifications of the light source of the OLT stage 10 is increased, the price is increased, on the other hand There is a problem that the intensity of the optical signal passing through the optical fiber is not increased due to the stimulated Brillouin scattering (SBS) phenomenon that may occur when the optical signal having a narrow line width and a high intensity is incident on the optical fiber. That is, when the intensity of the incident optical signal is greater than the SBS threshold, a part of the intensity of the incident optical signal returns to the direction opposite to the traveling direction.

2 is a graph illustrating an example in which the intensity of light output by the SBS phenomenon does not increase even when the intensity of light incident on the optical fiber is increased.

Therefore, the use of a low intensity light source is convenient for system configuration, but has a problem in that the transmission distance is limited.

The present invention has been made to solve the above-mentioned problems, and by using a remote pumping optical amplifier to increase the transmission distance of the PON system, it is possible to amplify the optical signal, so that long-distance transmission is possible, and at the RN stage It is an object of the present invention to provide a passive optical subscriber network system using a remote-pumped optical amplifier, which is easy to maintain due to no power, thereby enabling the construction of an economical long-range PON system.

In the passive optical subscriber network system using the remote pumping optical amplifier according to the present invention for achieving the above object, in the passive optical subscriber network system in which the optical line terminator (OLT) stage and the remote node (RN) stage are connected by optical fibers, The OLT stage includes a pumping light source for pumping EDF, and the RN stage includes an EDF (Erbium-doped fiber).

The remote pumping optical amplifier may be a bidirectional remote pumping optical amplifier for simultaneously amplifying an uplink optical signal and a downlink optical signal, or a bidirectional remote pumping optical amplifier for simultaneously amplifying a C-band downlink optical signal and an L-band uplink optical signal. It is preferable that the bidirectional remote pumping optical amplifier amplify the L-band downlink optical signal and the C-band uplink optical signal at the same time, or the unidirectional remote pumping optical amplifier selectively amplifying only the uplink optical signal or the downlink optical signal.

In addition, a C / L-band WDM coupler is provided in front of and behind the EDF to bypass the uplink or downlink optical signal, and to bypass the uplink or downlink optical signal. An optical circulator is provided before and after the EDF.

In addition, a plurality of remote pumping optical amplifiers are provided to amplify each signal when the uplink and downlink optical signals use different optical paths, and excess pumping is performed at an output stage to increase pumping efficiency of the remote pumping optical amplifier. And an optical fiber grating for reincident light.

The pumping light source is more preferably 1480 nm pump LD.

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

3 shows an optical communication system using a remote pumping optical amplifier according to the present invention.

As shown, reference numeral 20 denotes an optical transmitter, 21 an pump light source (Pump LD), 22 an EDF, and 23 an optical receiver.

In general, the wavelength band of light for pumping the EDF uses the 980 nm band and 1480 nm band. In terms of pumping efficiency, the 980 nm band is good, but the loss of the 980 nm band in the optical fiber is about 1 dB / km, which is very large, making it unsuitable for the pump light source of the remote pumping optical amplifier.

The present invention proposes a remote pumping optical amplification system using 1480 nm pump LD and EDF.

As shown, the remote pumping optical amplifier of the present invention is an optical fiber (Erbium-doped fiber) (EDF) 22 to which dozens of meters of erbium is added between the optical transmitters 20 and 23 and 1480 nm for remotely pumping the same. Band pumping light source (pump LD) 21 is used.

In single-mode fiber, the loss in the 1480 nm band is about 0.3 dB / km. Thus, when 200 mW of light at 1480 nm passes through 10 km of a single-mode fiber, half the loss is lost and 100 mW of light enters the EDF, enabling optical amplification.

<First Embodiment>

4 is a block diagram showing the structure of a PON system using a remote pumping optical amplifier according to a first embodiment of the present invention.

As shown, reference numeral 30 is an OLT, 31 is a pump light source (Pump LD), 33 is an EDF, 32 is a WDM coupler, 34 is an RN, and 35 is an ONU.

In the first embodiment of the present invention, 1480 nm pump LD is added to the OLT stage 30 as a pumping light source 31 for remotely pumping the EDF 33, and an EDF 33 is added to the RN stage 34. Structure.

The light output from the 1480 nm pump LD 31 is coupled to the single mode optical fiber through the WDM coupler 32 and transmitted to the ONU stage 35 simultaneously with the downlink optical signal.

The pumped light passing through the single mode optical fiber is absorbed by the EDF 33 to generate the density inversion of the EDF 33, and the downward optical signal is amplified while passing through the EDF 33.

Since the pumping light source 31 is mostly absorbed by the EDF 33, only the downlink optical signal amplified by the EDF 33 is distributed in the RN stage 34, rather than being transmitted to the ONU stage 35. Is sent).

FIG. 5 is a graph illustrating a change in intensity of a downlink optical signal according to an expected distance in a PON system using a remote pumping optical amplifier of the present invention and a PON system that is not.

As shown, the signal strength in a typical PON system is indicated by a dotted line and the signal strength in a PON system using a remote pumping optical amplifier according to the present invention is indicated by a solid line. In the case of not using the remote pumping optical amplifier, the downlink optical signal suffers loss at the RN stage 34, and the signal becomes smaller, whereas in the case of using the remote pumping optical amplifier, the downlink optical signal is gained and the final ONU stage (35). ), The difference in signal strength increases by the gain of the remote-pumped optical amplifier, allowing longer distance transmission.

In addition, the remote pumping optical amplifier is capable of unidirectional amplification or bidirectional amplification depending on the configuration, so if the bidirectional amplification is configured, the uplink optical signal as well as the downlink optical signal can be amplified.

In the PON system according to the present invention, the wavelength of the downlink optical signal and the wavelength of the uplink optical signal may be operated using different wavelength bands. In this case, in the structure according to the first embodiment, both the uplink signal and the downlink signal share a remote pumping optical amplifier.

EDF using a 1480 nm pumping light source can amplify only C-band (1530 nm to 1565 nm) or L-band (1570 nm to 1605 nm), depending on the strength of the pump and the length of the EDF. The signal of can be absorbed in the EDF. Of course, when the required signal gain is small and the length of the EDF is short, the degree of absorption and amplification in the L-band is small and there is no problem in use. However, if the gain of the required amplifier is large, the length of the EDF must be relatively long. Therefore, when the L-band signal is input, it can be absorbed without being amplified in the EDF.

In order to solve this problem, a method of selectively bypassing one band of a C-band signal or an L-band signal is required.

Second Embodiment

6 shows a remote pumping optical amplifier when the wavelength band of the downlink optical signal of the present invention is C-band (1530 nm ~ 1565 nm) and the wavelength band of the uplink optical signal is L-band (1570 nm ~ 1605 nm). A block diagram showing a second embodiment of the invention for the following.

As shown, 40 is an OLT, 41 is a pump light source (Pump LD), 44 is an EDF, 42 is a WDM coupler, 46 is an RN, 47 is an ONU, 43 and 45 are C / L-band WDM couplers.

In the present invention, the C-band downlink optical signal and the 1480 nm pumped light are input to the EDF 44 through the C / L-band WDM coupler 43 and then amplified into the RN stage 46. The L-band uplink optical signal output from the ONU stage 47 is bypassed through the remote pumping optical amplifier using the C / L-band WDM coupler 45.

When amplifying the uplink optical signal without amplifying the downlink optical signal, the downlink optical signal may be bypassed or the wavelength band may be replaced.

7 is a block diagram showing a structure using an optical circulator according to a second embodiment of the present invention, wherein reference numeral 50 denotes an OLT, 51 denotes a pump light source (Pump LD), 54 denotes an EDF, 52 denotes a WDM coupler, 56 is RN, 57 is ONU, and 53 and 55 are optical circulators.

In another embodiment of the present invention, the optical circulators 53 and 55 are used instead of the C / L-band WDM coupler 43 and 45 as a method of bypassing an uplink or downlink optical signal.

Third Embodiment

As described above, the first and second embodiments of the present invention have described a structure for amplifying an optical signal using a remote pumping optical amplifier in a PON system in which the downlink optical signal and the uplink optical signal share one optical fiber.

If the downlink and uplink signals do not share a single optical path and use different optical paths, two separate remote pumping optical amplifiers are required.

FIG. 8 is a block diagram showing the structure of a PON system using a remote pumping optical amplifier when the up-down signals of the present invention use different optical fibers.

As shown, reference numeral 60 denotes an OLT, 61, 67 denotes a WDM coupler, 62 denotes an EDF, 63 denotes an optical circulator, 64 denotes an RN, 65 denotes an ONU, 66 denotes a pump LD, and 69 denotes an upward optical signal. It is an optical path.

The uplink optical signal passes through the RN 64 and then enters the uplink optical signal path 69 using the optical circulator 63 and is amplified by a remote pumping optical amplifier. In this case, the use of an optical amplifier can be proposed if necessary.

The pumping light source 66 of each remote pumping optical amplifier may be located at the OLT stage 60, and the pumping light source output from one 1480 nm pump LD may be divided by 50:50.

Fourth Embodiment

9 is a block diagram showing the structure of a remote pumping optical amplifier using the optical fiber grating of the present invention.

As shown, the pumping light source in the 1480 nm band used as the light source of the remote pumping optical amplifier will mostly be absorbed by the EDF, but there may be excess pumping light that is not absorbed according to its intensity.

Therefore, in this case, as shown in FIG. 9, an optical fiber grating 73 reflecting only the 1480 nm band may be added to the rear end of the EDF 72 to increase the efficiency of the amplifier by re-entering the EDF 72.

In the drawings and specification, the best embodiments have been published. 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.

As described above, according to the passive optical subscriber network system using the remote pumping optical amplifier according to the present invention, it is very likely to be used as the next generation subscriber network system, and the demand of the PON system will increase rapidly in the near future. In addition, the PON system using the remote pumping optical amplifier according to the present invention adds only EDF to the RN stage without using an optical amplifier that requires power at the RN stage, and the pumping light source is OLT. By being located at the stage, there is an effect that the transmission distance can be increased by simply applying to a conventional PON system. In other words, the PON system using the remote pumping optical amplifier of the present invention can effectively increase the transmission distance of the PON system without requiring power at the RN stage, and thus has a very suitable effect for a long distance PON system.

Claims (10)

In a passive optical subscriber network system in which an optical line terminator (OLT) stage and a remote node (RN) stage, which are spaced apart over a long distance, are connected to each other by an optical fiber, The OLT stage includes a pumping light source for pumping Erbium-doped fiber (EDF), the RN stage includes an EDF, and the pumping light source is a passive light using a remote pumping optical amplifier, characterized in that 1480 nm pump LD. Subscriber Network System. The method of claim 1, The remote pumping optical amplifier is a passive optical subscriber network system using a remote pumping optical amplifier, characterized in that the bidirectional remote pumping optical amplifier for amplifying the uplink signal and the downlink optical signal at the same time. The method of claim 1, The remote pumping optical amplifier is a passive optical subscriber network system using a remote pumping optical amplifier, characterized in that the bi-directional remote pumping optical amplifier for amplifying the C-band downlink signal and the L-band uplink optical signal at the same time. The method of claim 1, The remote pumping optical amplifier is a passive optical subscriber network system using a remote pumping optical amplifier, characterized in that the bi-directional remote pumping optical amplifier for amplifying the L-band downlink signal and the C-band uplink optical signal at the same time. The method of claim 1, And said remote pumping optical amplifier is a unidirectional remote pumping optical amplifier for selectively amplifying only an uplink optical signal or a downlink optical signal. The method according to any one of claims 2 to 5, And a C / L-band WDM coupler in front of and behind the EDF for bypassing the uplink or downlink optical signal. The method according to any one of claims 2 to 5, Passive optical subscriber network system using a remote pumping optical amplifier, characterized in that it comprises an optical circulator before and after the EDF for bypassing the uplink or downlink optical signal. The method according to any one of claims 2 to 5, And a plurality of remote pumping optical amplifiers for amplifying each signal when the uplink optical signal and the downlink optical signal use different optical paths. The method according to any one of claims 1 to 5, Passive optical subscriber network system using a remote pumping optical amplifier characterized in that it comprises a fiber grating for re-injecting the excess pumping light to the output terminal in order to increase the pumping efficiency of the remote pumping optical amplifier. delete

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