CN102946273B - Fault detection method for optical fiber links of passive optical networks - Google Patents
Fault detection method for optical fiber links of passive optical networks Download PDFInfo
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Abstract
The invention discloses a fault detection method for optical fiber links of passive optical networks. The method comprises the following steps that: an optical encoder array is placed at a remote node, and after optical coded signals which are different and orthogonal to each other are generated at the remote node, the signals enter into each branch and continues to be transmitted; an optical reflector at the front end of an optical network unit of each branch reflects the optical coded signals back to a fault detection system of a central office; and in the fault detection system of the central office, the photoelectric conversion of the received optical coded signals is completed through a specific electric-domain decoding structure, and then received coded electric signals are processed by using a network recognition algorithm so as to analyze and judge the state of an optical fiber link. According to the invention, the complexity and difficulty of system implementation can be reduced; the decoding operation is completed in an electric domain, thereby improving the power budget of the fault detection system and reducing the system cost.
Description
Technical field
The present invention relates to a kind of EPON (PON) optical fiber link fault detection method, particularly relate to a kind of PON optical fiber link fault detection method of decoding based on pumped FIR laser and electrical domain, belong to technical field of optical fiber communication.
Background technology
Along with PON is widely used in optical access network, increasing concern is subject to the fault detect of the optical fiber link state in optical-fiber network.Optical fibre link circuit testing equipment conventional is at present optical time domain reflectometer (OTDR), but OTDR can only be applied in the optical fibre link circuit testing of point-to-point.In the PON adopting tree structure and optical power divider, the backward Rayleigh scattering that the detection light pulse that OTDR sends produces is the linear superposition of each branch road backscatter signal.Therefore, the branch road of None-identified guilty culprit, therefore directly cannot be applied in OTDR in PON fault detect.In the optical fiber link of PON, there is the close leg endpoint reflection event of many distances or tie point reflection event, this just requires that OTDR testing equipment has high range resolution ratio and short testing blind zone, thus can distinguish these different reflection events.Meanwhile, in PON, the optical power distributor of high splitting ratio brings high insertion loss, thus requires that OTDR has large dynamic range.But so far, OTDR technology wants to meet high range resolution ratio and large dynamic range is still very difficult simultaneously.
For large user's capacity (as 1:64,1:128 etc.) the optical fiber link fault detect of PON, PON fault detection method based on OTDR technology is difficult to the high power loss overcome because high splitting ratio brings, can only by changing the system configuration of distant-end node, increase Wavelength selective reflective device or adopt the fault detect of the method realizations such as poll fault detect to whole network, but the equal Shortcomings in aspect such as these methods are in system cost, real-time fault detect.In order to solve the optical fiber link fault detection problem of PON, researcher proposes and uses pumped FIR laser method to be applied to PON fault detect.As the periodic light decoding method that the people such as H.Fathallah propose, the method is that each optical network unit (ONU) distributes a unique light code word and carries out a line, an optical encoder is had in the front end of ONU, pumped FIR laser is carried out to fault detect light signal and is reflected back OLT, hold at OLT, photodissociation code is carried out to the pumped FIR laser signal of all ONU, by analytic solution code optical signal, fault detect is carried out to the optical fiber link of each branch road.But the cycle causes the increase of period distances while being coded in and producing a large amount of light code word, thus cause correlation distance to become large, make the interference between code word become large.
(application number is CN201110402605.X to a Chinese invention patent application, the applying date is on December 07th, 2011, publication number is CN102378072A, and publication date is on 03 14th, 2012) disclose " a kind of hop period light decoding method and optical encoder ".This light decoding method adopts the cycle to encode and frequency domain adopts frequency hopping to encode in time domain.Hop period light code word, while maintenance cardinality is large, has less correlation distance, can effectively suppress multi-user interference and beat noise, improves system failure detection performance.But the method exists a problem, namely need to add different optical encoders in different ONU front ends, thus use different light code words to identify different branch roads.This needs to carry out unified systems organization and installation through the workmen of professional training, and for the applied environment that PON user comparatively disperses, in the process that system is installed, still can bring certain difficulty.In addition, carry out decoding computing at receiving terminal by optica l decode, can bring larger optical power loss, and the volume of current optica l decode array is comparatively large, cost is higher.
Summary of the invention
The present invention proposes a kind of passive optical network optical fiber link failure detection method, mutually orthogonal and not identical pumped FIR laser is carried out to each ONU, receive at the pumped FIR laser coupled signal of receiving terminal to all ONU and analyze, thus detection fiber link failure, and the present invention overcomes the difficulty that prior art adopts different optical encoder to bring in ONU front end, by special design, optical encoder is placed on distant-end node place, thus ensures that ONU end equipment has homogeneity.This, by reducing the difficulty of System Implementation, is more suitable for the applied environment that PON user comparatively disperses.By electrical domain decode structures and Network Recognition algorithm, optica l decode array can be removed from receiving terminal, decoding computing is completed in electrical domain, thus improve the power budget of fault detection system and reduce system cost.
The present invention is concrete by the following technical solutions:
A kind of passive optical network optical fiber link failure detection method, comprises the following steps:
Detection light pulses machine in steps A, central office side fault detection system sends U wave band and detects light pulse signal, U wave band detects light pulse signal and is combined with data optical signal through the first smooth annular device and first wave division multiplexer successively, enters EPON transmission;
Step B, distant-end node place at EPON, by Second Wave division multiplexer, detection light pulse signal is separated with data optical signal, detect light pulse signal enter optical encoder array through optical power distributor and carry out branch road pumped FIR laser respectively, the branch road pumped FIR laser signal produced enters continuation transmission respectively by the wavelength division multiplexer of each branch road, the branch road pumped FIR laser signal entering different branch is different separately and mutually orthogonal, described pumped FIR laser adopts existing hop period pumped FIR laser method, and described each branch road pumped FIR laser signal is made up of pumped FIR laser subpulse;
Step C, the reflective optical system of U wave band is set respectively in the front end of the optical network unit of each branch road, and utilize the reflective optical system of each U wave band to reflect branch road pumped FIR laser signal, obtain branch road pumped FIR laser reflected signal, each branch road pumped FIR laser reflected signal is successively through wavelength division multiplexer and the light annular device of each branch road, and be coupled by optical power distributor and obtain pumped FIR laser reflection coupling signal, pumped FIR laser reflection coupling signal is got back in central office side fault detection system through Second Wave division multiplexer and first wave division multiplexer successively, around here, data optical signal keeps normal transmission,
Step D, in central office side fault detection system, the pumped FIR laser reflected signal received is after the first smooth annular device, two-way is divided into by 1:2 optical power distributor, one tunnel directly converts pumped FIR laser reflection coupling signal to coded reflective coupled electrical signal by photodiode, and pumped FIR laser reflection coupling signal is divided into the branch road of w different wave length by another route the 3rd wavelength division multiplexer, photodiode converts respectively by each branch road becomes each wavelength branch road signal of telecommunication, w is natural number, represents the total quantity of the wavelength that pumped FIR laser reflection coupling signal has;
Step e, utilize Network Recognition algorithm, fault detect is implemented to passive optical network optical fiber link
By the comparison to coded reflective coupled electrical signal and each wavelength branch road signal of telecommunication, obtain in coded reflective coupled electrical signal, each time-domain position being encoded the wavelength information of subpulse, and utilize the Network Recognition algorithm be built in Network Recognition module to carry out analyzing and processing to coded reflective coupled electrical signal, obtain the result to passive optical network optical fiber link implementing monitoring.
Network Recognition algorithm described in the fault detection method of passive optical network optical fiber link comprises the following steps:
Step e 1, using each branch road pumped FIR laser signal as elementary cell, the information of the elementary cell of each described branch road pumped FIR laser signal comprises time-domain position and the wavelength information of each coding subpulse, the first branch road pumped FIR laser signal is represented with the first elementary cell, second elementary cell represents the second branch road pumped FIR laser signal, the like, n-th elementary cell represents the n-th branch road pumped FIR laser signal, n is natural number, represent the branch road quantity in network, all elementary cells are stored in the database of Network Recognition algorithm;
Step e 2, by the comparison to coded reflective coupled electrical signal and each wavelength branch road signal of telecommunication, the wavelength information of the subpulse that obtains in coded reflective coupled electrical signal, each time-domain position being encoded;
Step e 3, coded reflective coupled electrical signal to be analyzed, if two or more coding subpulses are overlapping in time domain, then these coding subpulses that time domain overlap occurs are placed in noisy coding subpulse signal set, if coding subpulse is not overlapping in time domain, then the coding subpulse that time domain overlap these is not occurred is placed in glitch-free coding subpulse signal set;
Step e 4, the first elementary cell in Network Recognition algorithm data-base and glitch-free coding subpulse signal set are compared, if the time-domain position of the coding subpulse in glitch-free coding subpulse signal set is consistent with the first elementary cell with wavelength information, then judge that the coding subpulse in the glitch-free coding subpulse signal set consistent with the first elementary cell formed through reflecting back into central office by the first elementary cell, remove reflecting back into the coding subpulse that central office formed from glitch-free coding subpulse signal set and the first elementary cell is removed from the database of Network Recognition algorithm simultaneously,
Step e 5, to analogize according to method described in step e 4, process the second elementary cell successively ..., the coding subpulse in the n-th elementary cell and glitch-free coding subpulse signal set;
Step e 6, continue to utilize remaining elementary cell in database, elementary cell remaining in database is carried out combination in any, obtain the various compound modes of remaining elementary cell, coding subpulse in the coding subpulse do not removed in glitch-free coding subpulse signal set and noisy coding subpulse signal set is formed remaining coding subpulse, again coding subpulse remaining in the various compound mode of remaining elementary cell and coded reflective coupled electrical signal is compared, elementary cell corresponding to the compound mode of remaining elementary cell consistent with wavelength information for time-domain position and the coding subpulse in remaining coding subpulse are removed from glitch-free coding subpulse signal set and noisy coding subpulse signal set from database neutralization respectively, and, think that the coding subpulse removed from glitch-free coding subpulse signal set and noisy coding subpulse signal set is that elementary cell corresponding to the compound mode of the remaining elementary cell removed in database is formed through reflecting back into central office
The database of Network Recognition algorithm is analyzed, if (x is natural number also to remain xth elementary cell in database, value is between 0 to n), then illustrate that the code signal of xth branch road is not present in the coded reflective coupled electrical signal received, therefore judge that outage appears in the optical fiber link of xth branch road in EPON, can judge that the optical fiber link of the branch road corresponding to elementary cell be removed from database is normal simultaneously, if also remain all elementary cells in database, namely Network Recognition process does not remove any elementary cell, then judge that outage appears in the trunk optical fiber link of EPON.
Compared to existing technology, the present invention has following beneficial effect:
Different optical encoders is placed on the optical network unit front end of each branch road by 1, traditional hop period light encoding and decoding fault detection method, thus makes the device of optical network unit of each branch road different.And in actual applications, telecom operators wish to adopt identical device of optical network unit at each tributary user end, thus reduce the complexity of engineering construction and facilitate the management maintenance in later stage.By optical encoder is placed in distant-end node (such as, the equipment box place in residential building roadside), at the U wave band reflective optical system that the user side of each branch road only needs use one identical, maintain the homogeny of each branch road device of optical network unit, facilitate the installation of system and the final-period management of fault detect network to safeguard.
2, electrical domain decode structures is adopted at the receiving terminal of fault detection system, decrease optica l decode array, and the optical power distributor of high splitting ratio is instead of with wavelength division multiplexer, due to the low insertion loss of wavelength division multiplexer, significantly reduce the optical power budget of fault detection system, thus make fault detection system can support the passive optical network optical fiber link failure detection of higher user capacity or more longer transmission distance.In addition, instead of expensive optical device with the electric device of embedded with network identification module, reduce the cost of fault detection system.
Accompanying drawing explanation
Fig. 1 is the flow chart of passive optical network optical fiber link failure detection method of the present invention;
Fig. 2 is the system configuration schematic diagram adopting area of light decoding scheme;
Fig. 3 is the system configuration schematic diagram of passive optical network optical fiber link failure detection method of the present invention;
Fig. 4 is Network Recognition algorithm principle figure;
Fig. 5 is Network Recognition algorithm steps 2 principle schematic;
Fig. 6 is Network Recognition algorithm examples schematic diagram;
Fig. 7 is checking experimental system structure chart;
Fig. 8 is confirmatory experiment test result.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is described in detail:
Fig. 1 is the flow chart of passive optical network optical fiber link failure detection method of the present invention, comprises the following steps:
The fault detection system of step 1, central office side sends U wave band to EPON and detects light pulse signal;
Step 2, at distant-end node place, by wavelength division multiplexer, detection light pulse signal is separated with data optical signal, detection light pulse signal enters optical encoder array through optical power distributor and carries out pumped FIR laser, the pumped FIR laser signal produced enters different branch roads and continues transmission, and the pumped FIR laser signal entering different branch is different separately and mutually orthogonal;
Step 3, all have the reflective optical system of a U wave band in the front end of the optical network unit of each branch road, pumped FIR laser signal is launched back the fault detection system of central office side, and data optical signal without interruption can normal transmission;
Step 4, in the fault detection system of central office side, the pumped FIR laser reflection coupling signal received carries out opto-electronic conversion through the specific structure that receives, the signal of telecommunication after conversion carries out analyzing and processing by the Network Recognition algorithm being built in Network Recognition module, obtains the optical fiber link state of branch road residing for each optical network unit.
Fig. 2 is the light encoding and decoding schematic diagram in traditional pumped FIR laser fault detection method.As seen from the figure, at the receiving terminal of fault detection system, by all coded light signal after optical power distributor, enter optica l decode array and carry out photodissociation code, opto-electronic conversion is carried out again by photodiode, by observing the state of the decoding autocorrelation signal of each branch road, fault detect can be carried out to the optical fiber link of PON.But the use of optical power distributor brings larger power loss, and the cost of optical device is higher.Place different optical encoders in the optical network unit front end of each branch road, bring the inconsistency of ustomer premises access equipment, be unfavorable for that the construction of system and final-period management are safeguarded.
Fig. 3 is the system configuration schematic diagram of passive optical network optical fiber link failure detection method of the present invention.Detection light pulses machine in steps A, central office side fault detection system sends U wave band and detects light pulse signal, U wave band detects light pulse signal and is combined with data optical signal through the first smooth annular device and first wave division multiplexer successively, enters EPON transmission.
Step B, distant-end node place at EPON, by Second Wave division multiplexer, detection light pulse signal is separated with data optical signal, detect light pulse signal enter optical encoder array through optical power distributor and carry out branch road pumped FIR laser respectively, the branch road pumped FIR laser signal produced enters continuation transmission respectively by the wavelength division multiplexer of each branch road, the branch road pumped FIR laser signal entering different branch is different separately and mutually orthogonal, described pumped FIR laser adopts existing hop period pumped FIR laser method, and described each branch road pumped FIR laser signal is made up of pumped FIR laser subpulse.
Step C, the reflective optical system of U wave band is set respectively in the front end of the optical network unit of each branch road, and utilize the reflective optical system of each U wave band to reflect branch road pumped FIR laser signal, obtain branch road pumped FIR laser reflected signal, each branch road pumped FIR laser reflected signal is successively through wavelength division multiplexer and the light annular device of each branch road, and be coupled by optical power distributor and obtain pumped FIR laser reflection coupling signal, pumped FIR laser reflection coupling signal is got back in central office side fault detection system through Second Wave division multiplexer and first wave division multiplexer successively, around here, data optical signal keeps normal transmission.
Step D, in central office side fault detection system, the pumped FIR laser reflected signal received is after the first smooth annular device, two-way is divided into by 1:2 optical power distributor, one tunnel directly converts pumped FIR laser reflection coupling signal to coded reflective coupled electrical signal by photodiode, and pumped FIR laser reflection coupling signal is divided into the branch road of w different wave length by another route the 3rd wavelength division multiplexer, photodiode converts respectively by each branch road becomes each wavelength branch road signal of telecommunication, w is natural number, represents the total quantity of the wavelength that pumped FIR laser reflection coupling signal has.
Step e, utilize Network Recognition algorithm, fault detect is implemented to passive optical network optical fiber link.By the comparison to coded reflective coupled electrical signal and each wavelength branch road signal of telecommunication, obtain in coded reflective coupled electrical signal, each time-domain position being encoded the wavelength information of subpulse, and utilize the Network Recognition algorithm be built in Network Recognition module to carry out analyzing and processing to coded reflective coupled electrical signal, obtain the result to passive optical network optical fiber link implementing monitoring.
Fig. 4 is the Network Recognition algorithm principle figure in passive optical network optical fiber link failure detection method, comprises the following steps:
Step e 1, using each branch road pumped FIR laser signal as elementary cell, the information of the elementary cell of each described branch road pumped FIR laser signal comprises time-domain position and the wavelength information of each coding subpulse, the first branch road pumped FIR laser signal is represented with the first elementary cell, second elementary cell represents the second branch road pumped FIR laser signal, the like, n-th elementary cell represents the n-th branch road pumped FIR laser signal, n is natural number, represent the branch road quantity in network, all elementary cells are stored in the database of Network Recognition algorithm;
Step e 2, by the comparison to coded reflective coupled electrical signal and each wavelength branch road signal of telecommunication, the wavelength information of the subpulse that obtains in coded reflective coupled electrical signal, each time-domain position being encoded;
Step e 3, coded reflective coupled electrical signal to be analyzed, if two or more coding subpulses are overlapping in time domain, then these coding subpulses that time domain overlap occurs are placed in noisy coding subpulse signal set, if coding subpulse is not overlapping in time domain, then the coding subpulse that time domain overlap these is not occurred is placed in glitch-free coding subpulse signal set;
Step e 4, the first elementary cell in Network Recognition algorithm data-base and glitch-free coding subpulse signal set are compared, if the time-domain position of the coding subpulse in glitch-free coding subpulse signal set is consistent with the first elementary cell with wavelength information, then judge that the coding subpulse in the glitch-free coding subpulse signal set consistent with the first elementary cell formed through reflecting back into central office by the first elementary cell, remove reflecting back into the coding subpulse that central office formed from glitch-free coding subpulse signal set and the first elementary cell is removed from the database of Network Recognition algorithm simultaneously,
Step e 5, to analogize according to method described in step e 4, process the second elementary cell successively ..., the coding subpulse in the n-th elementary cell and glitch-free coding subpulse signal set;
Step e 6, continue to utilize remaining elementary cell in database, elementary cell remaining in database is carried out combination in any, obtain the various compound modes of remaining elementary cell, coding subpulse in the coding subpulse do not removed in glitch-free coding subpulse signal set and noisy coding subpulse signal set is formed remaining coding subpulse, again coding subpulse remaining in the various compound mode of remaining elementary cell and coded reflective coupled electrical signal is compared, elementary cell corresponding to the compound mode of remaining elementary cell consistent with wavelength information for time-domain position and the coding subpulse in remaining coding subpulse are removed from glitch-free coding subpulse signal set and noisy coding subpulse signal set from database neutralization respectively, and, think that the coding subpulse removed from glitch-free coding subpulse signal set and noisy coding subpulse signal set is that elementary cell corresponding to the compound mode of the remaining elementary cell removed in database is formed through reflecting back into central office
The database of Network Recognition algorithm is analyzed, if (x is natural number also to remain xth elementary cell in database, value is between 0 to n), then illustrate that the code signal of xth branch road is not present in the coded reflective coupled electrical signal received, therefore judge that outage appears in the optical fiber link of xth branch road in EPON, can judge that the optical fiber link of the branch road corresponding to elementary cell be removed from database is normal simultaneously, if also remain all elementary cells in database, namely Network Recognition process does not remove any elementary cell, then judge that outage appears in the trunk optical fiber link of EPON.
Described pumped FIR laser adopts hop period pumped FIR laser method to carry out pumped FIR laser.Hop period light decoding method carries out encoding and decoding in time domain and frequency domain simultaneously, and light code word carries out cycle encoding and decoding in time domain, carries out frequency hopping encoding and decoding at frequency domain.Concrete decoding method can (application number be CN201110402605.X with reference to a Chinese invention patent application, the applying date is on December 07th, 2011, publication number is CN102378072A, and publication date is on 03 14th, 2012) disclose " a kind of hop period light decoding method and optical encoder ".
Fig. 5 is Network Recognition algorithm steps E2 principle schematic.In the fault detection system of central office side, the pumped FIR laser signal of all branch roads received is after light annular device, two-way is divided into by 1:2 optical power distributor, one tunnel directly enters the coded electrical signal that photodiode converts becomes all branch roads, and separately lead up to wavelength division multiplexer and be divided in this example of 7(, suppose that the quantity of the wavelength sheet had in pumped FIR laser signal is 7) branch road of individual different wave length becomes each wavelength branch road signal of telecommunication respectively by the photodiode converts of each branch road.As shown in the figure, first via signal is the coded electrical signal figure of all branch roads, is formed by stacking by the coded electrical signal of each branch road.The signal of telecommunication of wavelength branch roads different for the coded electrical signal of all branch roads and other 7 is compared, on first time slot position of the coded electrical signal of all branch roads, have two subpulses of encoding, and at wavelength be the wavelength tributary signal of λ 4 and λ 7 first time slot position on have a subpulse signal of encoding respectively.The wavelength of the coding subpulse on first time slot position of the therefore coded electrical signal of known all branch roads is respectively λ 4 and λ 7.The like, the wavelength information of subpulse of can determining in the coded electrical signal figure of all branch roads, each time-domain position to be encoded, thus the time-domain position and the wavelength information that obtain each coding subpulse of the coded electrical signal of all branch roads.
Fig. 6 is Network Recognition algorithm examples schematic diagram.Suppose that PON exists 4 branch roads, native system adopts corresponding four branch roads of four code words to carry out pumped FIR laser, hop period light code word is respectively { (7,4), 4}, { (4,1), 5}, { (6,3), 4} and { (5,2), 9}.As above-mentioned Network Recognition algorithm, by the pumped FIR laser signal { (7,4) of the first branch road, 4} is defined as the first elementary cell, by the pumped FIR laser signal { (4,1) of the second branch road, 5} is defined as the second elementary cell, by the pumped FIR laser signal { (6,3) of the 3rd branch road, 4} is defined as the 3rd elementary cell, by the pumped FIR laser signal of the 4th branch road (5,2), 9} is defined as the 4th elementary cell, all exist in the database of Network Recognition algorithm, as shown in Fig. 6 left side.Suppose that the signal that receives at place of central office as shown in Figure 4, and through the step e 1 of Network Recognition algorithm and E2, obtained time-domain position and the wavelength information of each coding subpulse of the coded electrical signal of all branch roads.By Network Recognition algorithm steps E3, the set of noiseless coding subpulse can be obtained as shown in Fig. 6 right side.Elementary cell in database and the set of noiseless coding subpulse are compared successively, can draw in the signal received to there is the 4th elementary cell.The coding subpulse signal of the 4th elementary cell is removed from noiseless coding subpulse set, the 4th elementary cell is removed from database simultaneously.Other coding subpulses can not mate with elementary cell, therefore by the subpulse signal of None-identified and noisy coding subpulse signal combination, obtain the set of remaining coding subpulse.
Elementary cell remaining in database is carried out the various compound modes that combination in any (presence or absence and the elementary cell that comprise elementary cell are in different time-domain positions) obtains remaining elementary cell, successively the various compound mode of remaining elementary cell and remaining coding subpulse are compared, the first elementary cell can be obtained and the second elementary cell is in the first time slot simultaneously, the non-existent this compound mode of 3rd elementary cell, and this compound mode is mated completely with the set of remaining coding subpulse, determine the composition structure of remaining coding subpulse set thus.
By said process, Network Recognition algorithm can judge that in the coded reflective coupled electrical signal received, the first elementary cell and the second elementary cell are in the first time slot, and the 4th elementary cell is in the second time slot, and the signal of the 3rd elementary cell does not exist.Namely illustrate that the optical fiber link of the first, two and four branch road is in good condition.And outage appears in the optical fiber link of the 3rd branch road, therefore can not receive in central office the branch road pumped FIR laser signal that this branch road reflects.
Fig. 7 checking experimental system structure chart.In order to verify the feasibility of Network Recognition algorithm of the present invention further, carried out following test: by optical modulator, it is 1ns that wideband light source modulation is produced pulse duration, and repetition rate is that the broadband spectral of 10kHz detects light pulse sequence.Wide band detection light pulse sequence enters 20km optical fiber by image intensifer and optical circulator successively and transmits, optical encoder array is entered by 1:4 optical power distributor, optical encoder array to detection light pulse carry out pumped FIR laser after and reflect, the pumped FIR laser signal of 4 branch roads is coupled by 1:4 optical power distributor, is got back to the receiving terminal of fault detection system successively by 20km optical fiber and light annular device.At receiving terminal, the pumped FIR laser signal of 4 branch roads is divided into two-way by power splitter, and a road directly becomes the signal of telecommunication by photodiode converts, and another road is divided into the branch road of 7 different wave lengths through wavelength division multiplexer.All branch road interconnection network identification modules process.
In this experiment, adopt hop period light code word scheme, parameter choose is q=7, w=2, and the centre wavelength of seven wavelength available sheets is chosen as λ
1=1548.8nm, λ
2=1549.2nm, λ
3=1549.6nm, λ
4=1550nm, λ
5=1550.4nm, λ
6=1550.8nm, λ
7=1551.2nm.Four ONU hop period light code word used is respectively { (4,1), 5}, { (7,4), 5}, { (2,6), 4}, { (4,1), 9}, wherein (4,1), (7,4), (2,6) frequency hop sequences selected by frequency domain is represented, the periodic quantity of 4,5 and 9 expression time domain codings.Optical encoder is by two centre wavelength differences, optical fiber bragg grating FBG at a distance of certain length fiber delay line is in series, wherein the 3dB reflection spectrum width of FBG is about 0.2nm, and reflectivity is about 95%, and the length of fiber delay line is that 50cm and 90cm corresponds to periodic quantity 5 and 9.
Fig. 8 is experimental results, and use the pumped FIR laser signal of sampling oscilloscope to each branch road to test, obtain the coded electrical signal figure of each branch road, the average time of sampling oscilloscope is 256, for removing noise.Fig. 8 (b), (c), (d) and (e) is light code word { (4 respectively, 1), 5}, { (7,4), 5}, { (2,6), 4}, { (4,1), the coded electrical signal figure that 9} place branch road produces, can be used as elementary cell, for carrying out Network Recognition algorithm.Fig. 8 (a) is the coded electrical signal oscillogram of all branch roads received, structure is received by the experiment electrical domain decoding described in Fig. 4, time-domain position and the wavelength information of each coding subpulse in the coded electrical signal oscillogram of all branch roads can be determined, as shown in mark in Fig. 8 (a).Described in Fig. 5, complete the first two step of Network Recognition algorithm.Carry out the step 3 of Network Recognition algorithm, from Fig. 8 (a), can find out that most coding subpulse creates superposition in time domain, noisy coding subpulse signal can be divided into, only have 1 wavelength to be λ
1coding subpulse be glitch-free.By with the comparing of each branch road coded electrical signal elementary cell, can not determine that wavelength is λ
1coding subpulse be the coded electrical signal belonging to which branch road.Utilize the coded electrical signal elementary cell of 4 branch roads, adopt Network Recognition algorithm steps 5, coding subpulses all in Fig. 8 (a) is analyzed, by coded electrical signal elementary cell (i.e. Fig. 8 (b) of each branch road, (c), (d) and (e)) various possible assembled state and Fig. 8 (a) in all coding subpulse signal graph compare.The composition situation determining coding subpulses all in Fig. 8 (a) is { (4,1), 5}, { (7,4), 5} and (2,6), the coded electrical signal of 4} tri-light code words constitutes first peak in Fig. 8 (a) jointly, also illustrate that this leg length corresponding to three light code words is almost consistent, and { (4,1), the branch road coded electrical signal corresponding to 9} light code word is the wavelength after falling behind the first peak 3.7ns in Fig. 8 (a) is λ
4coding subpulse and last wavelength be λ
1coding subpulse.And (4,1), the leg length corresponding to 9} light code word corresponds to the 3.7ns in Fig. 8 (a) than the long 37cm(of other branch road).Coded electrical signal figure in Fig. 8 (a) is made up of jointly the coded electrical signal figure of 4 light code word place branch roads, illustrates that the optical fiber link of 4 branch roads is all normal.
Claims (1)
1. a passive optical network optical fiber link failure detection method, is characterized in that, comprises the following steps:
Detection light pulses machine in steps A, central office side fault detection system sends U wave band and detects light pulse signal, U wave band detects light pulse signal and is combined with data optical signal through the first smooth annular device and first wave division multiplexer successively, enters EPON transmission;
Step B, distant-end node place at EPON, by Second Wave division multiplexer, detection light pulse signal is separated with data optical signal, detect light pulse signal enter optical encoder array through optical power distributor and carry out branch road pumped FIR laser respectively, the branch road pumped FIR laser signal produced enters continuation transmission respectively by the wavelength division multiplexer of each branch road, the branch road pumped FIR laser signal entering different branch is different separately and mutually orthogonal, described pumped FIR laser adopts existing hop period pumped FIR laser method, and described each branch road pumped FIR laser signal is made up of pumped FIR laser subpulse;
Step C, the reflective optical system of U wave band is set respectively in the front end of the optical network unit of each branch road, and utilize the reflective optical system of each U wave band to reflect branch road pumped FIR laser signal, obtain branch road pumped FIR laser reflected signal, each branch road pumped FIR laser reflected signal is successively through wavelength division multiplexer and the light annular device of each branch road, and be coupled by optical power distributor and obtain pumped FIR laser reflection coupling signal, pumped FIR laser reflection coupling signal is got back in central office side fault detection system through Second Wave division multiplexer and first wave division multiplexer successively, around here, data optical signal keeps normal transmission,
Step D, in central office side fault detection system, the pumped FIR laser reflected signal received is after the first smooth annular device, two-way is divided into by 1:2 optical power distributor, one tunnel directly converts pumped FIR laser reflection coupling signal to coded reflective coupled electrical signal by photodiode, and pumped FIR laser reflection coupling signal is divided into the branch road of w different wave length by another route the 3rd wavelength division multiplexer, photodiode converts respectively by each branch road becomes each wavelength branch road signal of telecommunication, w is natural number, represents the total quantity of the wavelength that pumped FIR laser reflection coupling signal has;
Step e, utilize Network Recognition algorithm, fault detect implemented to passive optical network optical fiber link:
By the comparison to coded reflective coupled electrical signal and each wavelength branch road signal of telecommunication, obtain in coded reflective coupled electrical signal, each time-domain position being encoded the wavelength information of subpulse, and utilize the Network Recognition algorithm be built in Network Recognition module to carry out analyzing and processing to coded reflective coupled electrical signal, obtain the result to passive optical network optical fiber link implementing monitoring;
Described Network Recognition algorithm comprises the following steps:
Step e 1, using each branch road pumped FIR laser signal as elementary cell, the information of the elementary cell of each described branch road pumped FIR laser signal comprises time-domain position and the wavelength information of each coding subpulse, the first branch road pumped FIR laser signal is represented with the first elementary cell, second elementary cell represents the second branch road pumped FIR laser signal, the like, n-th elementary cell represents the n-th branch road pumped FIR laser signal, n is natural number, represent the branch road quantity in network, all elementary cells are stored in the database of Network Recognition algorithm;
Step e 2, by the comparison to coded reflective coupled electrical signal and each wavelength branch road signal of telecommunication, the wavelength information of the subpulse that obtains in coded reflective coupled electrical signal, each time-domain position being encoded;
Step e 3, coded reflective coupled electrical signal to be analyzed, if two or more coding subpulses are overlapping in time domain, then these coding subpulses that time domain overlap occurs are placed in noisy coding subpulse signal set, if coding subpulse is not overlapping in time domain, then the coding subpulse that time domain overlap these is not occurred is placed in glitch-free coding subpulse signal set;
Step e 4, the first elementary cell in Network Recognition algorithm data-base and glitch-free coding subpulse signal set are compared, if the time-domain position of the coding subpulse in glitch-free coding subpulse signal set is consistent with the first elementary cell with wavelength information, then judge that the coding subpulse in the glitch-free coding subpulse signal set consistent with the first elementary cell formed through reflecting back into central office by the first elementary cell, remove reflecting back into the coding subpulse that central office formed from glitch-free coding subpulse signal set and the first elementary cell is removed from the database of Network Recognition algorithm simultaneously,
Step e 5, to analogize according to method described in step e 4, process the second elementary cell successively ..., the coding subpulse in the n-th elementary cell and glitch-free coding subpulse signal set;
Step e 6, continue to utilize remaining elementary cell in database, elementary cell remaining in database is carried out combination in any, obtain the various compound modes of remaining elementary cell, coding subpulse in the coding subpulse do not removed in glitch-free coding subpulse signal set and noisy coding subpulse signal set is formed remaining coding subpulse, again coding subpulse remaining in the various compound mode of remaining elementary cell and coded reflective coupled electrical signal is compared, elementary cell corresponding to the compound mode of remaining elementary cell consistent with wavelength information for time-domain position and the coding subpulse in remaining coding subpulse are removed from glitch-free coding subpulse signal set and noisy coding subpulse signal set from database neutralization respectively, and, think that the coding subpulse removed from glitch-free coding subpulse signal set and noisy coding subpulse signal set is that elementary cell corresponding to the compound mode of the remaining elementary cell removed in database is formed through reflecting back into central office
The database of Network Recognition algorithm is analyzed, if also remain xth elementary cell in database, then illustrate that the code signal of xth branch road is not present in the coded reflective coupled electrical signal received, therefore judge that outage appears in the optical fiber link of xth branch road in EPON, can judge that the optical fiber link of the branch road corresponding to elementary cell be removed from database is normal simultaneously, if also remain all elementary cells in database, namely Network Recognition process does not remove any elementary cell, then judge that outage appears in the trunk optical fiber link of EPON.
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