KR101021408B1 - Method for Monitoring Optical Fiber Line of WDM-PON Access Network - Google Patents

Abstract

In the passive optical optical network of wavelength division multiplexing system, where n signal beams having different wavelengths are combined and transmitted through one trunk beam and the signal beam is split and transmitted, the presence or absence of abnormality in each distribution beam is monitored. A method is provided. The monitoring method comprises the steps of generating and combining the supervisory light having n different wavelengths, demultiplexing the supervised supervisory light into n individual supervisory light having different wavelengths, and each branched by demultiplexing. Transmitting the individual monitoring beams through the respective distribution beams, backscattering or reflecting the individual monitoring beams on each of the distribution beams, and combining the individual monitoring beams backscattered and transmitted from the respective distribution beams to monitor one. Multiplexing the light, and analyzing the combined surveillance light to determine whether there is an abnormality in each of the split light paths. In this method, the individual monitoring light and the signal light transmitted through each distribution beam have different wavelengths.

Wavelength Division Multiplexing, Beam Monitoring, Backscattered Light Meters, OTDR

Description

Wavelength monitoring method of wavelength division multiplexing passive optical network {Method for Monitoring Optical Fiber Line of WDM-PON Access Network}             

1 shows a monitoring apparatus according to the prior art for checking the location and failure of the optical path failure in the passive optical network of the wavelength division multiplexing method,

2 schematically shows a configuration of an optical network for applying the monitoring method according to the present invention,

3 shows the spectrum of the light source of the monitoring device according to the invention,

4 is a view for explaining the operation of the arrayed waveguide grating for monitoring light in the optical network having the configuration shown in FIG.

The present invention relates to a light path monitoring method capable of quickly detecting an abnormality in the event of a failure of an optical cable in a wavelength division multiplexing passive optical network. The present invention relates to a method for monitoring an optical fiber that can identify whether there is a problem with the optical fiber at the same time with respect to the entire distributed optical fiber in the network.

Conventionally, a method for increasing a communication speed in an information communication network includes a method of increasing the speed of an electronic circuit (time division multiplexing (TDM)), a method of making an optically short pulse and multiplexing it (optical time division multiplexing, OTDM), and Wavelength division multiplexing (WDM), etc., in which different wavelengths are bundled and transmitted through one optical fiber, have been proposed. Among them, wavelength division multiplexing is intended to utilize the characteristics of optical fiber that can communicate over a wide frequency range.

FIG. 1 illustrates a configuration of a monitoring apparatus according to the prior art for checking the location and failure of a light path in a passive optical network (PON) to which the wavelength division multiplexing scheme is applied. As shown in FIG. 1, signal light having a plurality of different wavelengths generated by the signal light source 10 is combined and transmitted through one trunk path. An arrayed waveguide grating 20 (AWG) demultiplexes and splits the signal light transmitted through the trunk path into individual signal light having a plurality of different wavelengths. Each of the separated signal light is transmitted to the termination device 30 on the subscriber side through each distribution optical line. On the other hand, the backscattered light meter 40 has a wavelength variable function, and generates the monitoring light having one wavelength at a time and transmits it through the trunk line. The wavelength-division multiplexing apparatus 43 for monitoring light bypasses the array waveguide grating 20, and transmits monitoring light to the corresponding distribution beam. The surveillance light transmitted through the distribution beam is guided back along the distribution beam and reflected back by the surveillance light reflector 45 disposed at a suitable position in front of the termination device 30. The backscattered monitoring light is transmitted in a direction opposite to the propagation direction of the signal light and returns to the backscattered light measuring instrument 40. The monitoring light reflected back is analyzed to check whether there is an abnormality in the distribution beam. The backscattered light meter 40 sequentially checks whether there is an abnormality in each of the distribution beams while changing the wavelength of the monitoring light.

However, such a conventional monitoring device is not efficient because it can only check whether there is an abnormality in one distribution beam at a time, and there is a problem in that the price of equipment is increased because a backscattered light meter having a variable wavelength light source must be used.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an economically advantageous monitoring method which can confirm the presence or absence of any abnormality in all the distribution beams by one measurement.

According to the present invention, n signal lights having different wavelengths are combined to be transmitted from a station-side optical transmission apparatus through one trunk line, and each individual signal light separated from the combined signal light is transmitted to each subscriber side through n distribution beams. In the passive optical network of the wavelength division multiplexing method, there is provided a method for monitoring the presence or absence of an abnormality in each distribution beam. This monitoring method comprises the steps of: (a) the backscattered light meter simultaneously generating n individual monitoring lights having different wavelengths, and the wavelength division multiplexer combines them; and (b) Demultiplexing into n individual supervisory lights having wavelengths, (c) transmitting the n individual supervisory light beams branched by demultiplexing through the n distribution beams, and (d) A supervisory light reflector on the n distribution light beams backscatters or reflects the n individual monitoring light, and (e) the n individual monitoring light backscattered and transmitted on the n distribution light beams at the wavelength Splitting and multiplexing by the division multiplexing apparatus; and (f) analyzing the supervised light with which the backscattered light measuring device is combined to determine whether there are any abnormalities in the n distribution beams. It should. In this method, the individual monitoring light and the individual signal light transmitted through each distribution beam have different wavelengths.

FIG. 2 schematically shows the configuration of an optical network for applying the monitoring method according to the invention, FIG. 3 shows the spectrum of the light source of the monitoring device according to the invention, and FIG. 4 shows the configuration shown in FIG. It is a figure for demonstrating operation | movement of an arrayed waveguide grating in an optical network which has. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

In general, the passive optical network of the wavelength division multiplexing system has distribution beams such as 4, 8, 16, 32, 64 branches, etc. For convenience, the embodiment of the present invention will be described with reference to the optical network having four distribution beams. Explain.

As shown in FIG. 2, the passive optical network of the wavelength division multiplexing system has four signal light sources 10. Each signal light source generates signal light of different wavelengths. The signal light is combined and transmitted through the trunk line optical path from the station side optical transmission device, and is divided into four individual signal light by the grid light waveguide array 20 for the signal light. The distributed individual signal light is transmitted to the terminating device 30 on the subscriber side through each distributed light path.

The backscattered light measuring device 50 according to the present invention generates monitoring light having the same number of different wavelengths as the number of distribution beams included in the optical network of the wavelength division multiplexing method. That is, in this embodiment in which the signal light source 10 generates four signal lights, the backscattered light meter 50 provides monitoring light having four different wavelengths. The monitoring light is waveguided through the transmission-side wavelength division multiplexing device 41 and then guided to the trunk line, and is transmitted together with the signal beam through the trunk line. A first receiving side wavelength division multiplexing device 42 is disposed at the front end of the arrayed waveguide grating 20 for signal light, whereby the monitoring light is separated from the main optical path. The separated monitoring light is demultiplexed into four individual monitoring lights by the arraying waveguide grating 53 for monitoring light, and each individual monitoring light is guided to each of the distribution beams through the second receiving side wavelength division multiplexing device 44. The individual surveillance light transmitted through each distribution beam is guided back along the distribution beam and reflected by the surveillance light reflector 45 disposed at the front end of the termination device 30. The backscattered individual supervisory light is multiplexed through the second receiving side wavelength division multiplexing device 44 and the supervisory light arraying waveguide grating 53, and then waveguided into the trunk path through the first wavelength division multiplexing device 42. It is separated from the trunk line through the side wavelength division multiplexing device 41 and transmitted to the backscattered light meter 50. The backscattered light measuring device 50 analyzes the monitoring light reflected back and determines whether there is an abnormality in each distribution beam.

Preferably, the time taken for each individual monitoring light to be backscattered or reflected by the monitoring light reflector 45 in each of the distribution beams may be different for each distribution beam. For example, by varying the lengths of the distribution paths, the time required is adjusted differently. In this case, the waveform of the monitoring light output on the backscattered light measuring instrument 50 sequentially represents each event from the short distribution line to the long distribution line.

In the monitoring method according to the present invention, it is preferable to use a light source having a broad spectral characteristic as the monitoring light source of the backscattered light meter 50. In this embodiment, a Fabry-Perot laser diode is used as the monitoring light source. Fabry-Perot laser diodes are not suitable for amplification, but can get great power and generate supervised light with very broad spectral characteristics. The spectral characteristics of a typical Fabry-Perot laser diode are shown in FIG. 3. As shown in FIG. 3, the Fabry-Perot laser diode has a wide bandwidth, and a wavelength having a large power within the bandwidth appears at predetermined intervals. Therefore, it is good to use the light of the wavelength which power shows large as monitoring light. Since four supervisory lights are required in this embodiment, it is preferable to select four wavelengths around the center wavelength of the bandwidth as shown in FIG. A bandpass filter can be used to separate the monitoring light from the light source.

4 shows an arrayed waveguide grating 53 for monitoring light. The arrayed waveguide grating 53 for monitoring light preferably has the same free-spectral range (FSR) as the Fabry-Perot laser diode used as the light source of the backscattered light meter 50.

The arrayed waveguide gratings 20 and 53 are optical splitters fabricated by planar lightwave circuits (PLCs) that form optical waveguides using a large scale integrated circuit (LSI) fabrication technique on a quartz glass layer formed on a silicon substrate. Can be used. The planar lightwave circuit is composed of a plurality of channel waveguides of different lengths, an input / output waveguide and two fan waveguides. Although the planar lightwave circuit operates in the same way as a diffraction grating, it is possible to precisely add and separate high-density signals according to a precise waveguide design, to control transmission wavelength bands, and to be inexpensive because it is manufactured by LSI technology. .

The photosynthetic splitters currently used in wavelength division multiplexing systems include not only array waveguide gratings, but also combinations of dielectric multilayer filter, fiber brag grating (FBG), FBG and optical coupler. Technology, diffraction gratings, and the like. Therefore, a dielectric multilayer filter or the like can also be used as a supervisory light demultiplexer according to the number of channels used, and an optical demultiplexer can be selected according to the system specification according to the diversification of the wavelength division multiplexing system.

The technical spirit of the present invention has been described above with reference to the accompanying drawings, which describes exemplary embodiments of the present invention by way of example and does not limit the present invention. In addition, it is obvious that any person skilled in the art may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

The optical network monitoring method of the wavelength division multiplexing method according to the present invention can confirm the abnormality of all the distribution beams included in the optical network by one measurement, so that the optical network monitoring can be efficiently operated, and the wavelength variable light source It is economically advantageous because there is no need to use expensive equipment.

Claims (3)

N signal lights having different wavelengths outputted from the signal light source are combined and transmitted from the photonics-side optical transmission apparatus through one trunk line, and each individual signal light split from the combined signal light is transmitted to each subscriber side through n distribution optical lines. In the passive optical network of the wavelength division multiplexing method to monitor the presence or absence of abnormality in each distribution beam, (a) the backscattered light meter simultaneously generating n individual supervisory lights having different wavelengths and combining them by a wavelength division multiplexer; (b) demultiplexing the supervisory light with the arrayed waveguide grating into n individual supervisory lights having different wavelengths, (c) transmitting, by the arrayed waveguide grating, the n individual supervisory lights split by demultiplexing through the n distribution beams; (d) backscattering or reflecting the n individual surveillance lights by the surveillance light reflector on the n distribution beams; (e) the wavelength division multiplexer multiplexes and multiplexes the n individual supervisory lights transmitted backscattered on the n distribution beams, and (f) analyzing, by the counterscattered light meter, the combined light to determine whether there are any abnormalities in the n distribution beams, And the n individual monitoring light and the individual signal light transmitted through the n distribution beams have different wavelengths. The method according to claim 1, And wherein the time taken for the n individual monitoring lights to be guided along the n distribution beams to be backscattered or reflected back is different for each of the distribution beams. The method according to claim 1, And said n individual supervisory lights in step (a) are generated by a Fabry-Perot laser diode.

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