CN104660304B - A kind of coaxial network link-quality detection method initiated based on user terminal - Google Patents
A kind of coaxial network link-quality detection method initiated based on user terminal Download PDFInfo
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Abstract
The coaxial network link-quality detection method initiated based on user terminal that the present invention is provided, methods described is tested by initiating Time Domain Reflectometry at coaxial accessing user end, otdr signal is received at the coaxial accessing user end, according to the otdr signal of the corresponding coaxial cable received, the coaxial cable tested one by one in the coaxial network to coaxial access head end from the coaxial accessing user end is to judge whether to break down, and, when test is not broken down to wherein one coaxial cable and judges that the coaxial cable is connected with branch/distributor, analyze the branch/distributor with the impedance match situation of the tie point for the coaxial cable that is connected to determine link-quality according to the otdr signal of the correspondence branch/distributor, this method is initiated from subscriber household end, it is easy to the transmission quality of quick investigation coaxial network link standard coaxial cable and branch/distributor, it is convenient accurate, greatly increase broadband simultaneously, television services business added value.
Description
Technical field
The present invention relates to communication test technical field, more particularly to a kind of method of testing of coaxial network link-quality.
Background technology
With Two-way Reconstruction in CATV Network and Chinese Next generation broadcasting network (Next Generation
Broadcasting Network, NGB) build development, the biography that coaxial network link is registered one's residence as cable network final stage
Defeated medium, act as more and more important effect.NGB coaxial network not only carries One-to-All Broadcast television services, also by adopting
Transmit (Ethernet over Coax, EOC) or C-DOCSIS broadband access technologys to hold by coaxial cable with ether data
Two-way broadband business is carried, therefore, higher requirement is proposed to performance indications and link-quality of coaxial network etc..
Current network management system is only managed to the broadband access equipment that coaxial network is disposed, but is lacked to Coaxial Network
The devices such as coaxial cable, branch/distributor in road are monitored.If somewhere is broken down in coaxial network, tend not to
Immediately confirm it is that device fails or coaxial links break down, moreover, needing operation maintenance personnel with professional test instrument to now
Field is positioned manually, and so not only increase equipment is installed and O＆M cost, and operating efficiency is not high, solves the time of failure
It is long, so as to have impact on the satisfaction of user.
The time-domain measurement technique of existing Time Domain Reflectometry test (TDR) is mainly used in (such as twisted-pair feeder, same to single transmission medium
Shaft cable) measure to assess line quality, but lack the coaxial electric cable network to being made up of coaxial cable and branch/distributor
Network system link measuring method.And existing EOC technologies generally interoperate to calculate each work by EOC head ends and terminal
Frequency range SNR value, carries out coaxial links quality evaluation, can not be to link-quality although this method energy assessing link quality
Problem is reliably positioned, such as the problem of can not judging in coaxial links branch/distributor or coaxial cable is still made an uproar
The reason for sound.
The content of the invention
The shortcoming of prior art in view of the above, it is an object of the invention to provide it is a kind of based on user terminal initiate it is same
Axle network link quality detection method, branch/distributor or same in positioning coaxial links can not be detected for solving prior art
The problem of shaft cable signal transmission quality.
In order to achieve the above objects and other related objects, the present invention provides a kind of coaxial network chain initiated based on user terminal
Road quality determining method, the coaxial network is connected between coaxial access head end and coaxial accessing user end, methods described bag
Include：Time Domain Reflectometry test is initiated at the coaxial accessing user end；Otdr signal is received at the coaxial accessing user end；
According to the otdr signal of the corresponding coaxial cable received, head end is accessed one by one from the coaxial accessing user end to coaxial
The coaxial cable tested in the coaxial network arrives wherein one coaxial cable to judge whether to break down in test
When not breaking down and judging that the coaxial cable is connected with branch/distributor, according to the correspondence branch/distributor when
Domain reflected signal analyzes the branch/distributor with the impedance match situation of the tie point for the coaxial cable that is connected to determine link matter
Amount.
It is preferred that, the waving map signal of change of kth section coaxial cable initiating terminal is public from the coaxial accessing user end
Formula is：Wherein, the 1st section of coaxial cable starting from the coaxial accessing user end
End Time Domain Reflectometry test waving map signal of change formula be：uin(0)=∫ Uin(0)(f)×ej2πftdf；Wherein, uin(0)It is
The coaxial cable waving map signal amplitude, Uin(0)(f) it is test signal amplitude, f is frequency test signal, when t is test
Between point；
Wherein, according to the measurement range L between the coaxial access head end and coaxial accessing user end, test signal is selected
Step frequency Δ f；The Δ f is metWherein, vCoaxiallySpeed is transmitted for the medium signal of the known coaxial cable
Degree；According to presumptive test precision (ΔPrecision) selected test signal cut-off frequency FCut-off, meet condition：
It is preferred that, the otdr signal of the correspondence coaxial cable is correspondence from each impedance on the coaxial cable
Place is mismatched to produce.
It is preferred that, if the resistance from the coaxial accessing user end on kth bar coaxial cable, the kth bar coaxial cable
There are j at anti-mismatch, and kth bar coaxial cable described in cutting is j+1 sections, wherein, jth section impedance is designated as zk,j；J-th of resistance
The otdr signal that anti-mismatch place is produced feeds back to the calculation formula of the kth bar coaxial cable initiating terminal：
Wherein, lk,jFor jth section
Coaxial cable length；For reflectance factor, calculation formula is：
It is preferred that, the waving map signal of the kth bar coaxial cableDelayCalculation formula is：
The output signal of the kth bar coaxial cableCalculation formula is：
It is preferred that, according to the otdr signal received, from the coaxial accessing user end to coaxial access head end by
Bar tests in the coaxial network coaxial cable to judge whether to break down, including：Set the failure include open circuit, it is short
Road；The calculation formula of otdr signal under open circuit situation is obtained according to the otdr signal calculation formula： Time Domain Reflectometry under short circuit condition is obtained according to the otdr signal calculation formula
The calculation formula of signal：Wherein, α is signal in coaxial electrical
The attenuation coefficient of cable transmission；Comparison receives otdr signal and otdr signal, short circuit condition under the open circuit situation
Lower otdr signal, failure is judged when comparing consistent.
It is preferred that, it is described to judge that the coaxial cable is connected with branch/distributor, including：It is continuous in preset time period
More than two reflected signals are received, and reflected signal is fluctuated within the specific limits, then judges to be connected with branch/distributor.
It is preferred that, if k-th of branch/distributor includes 1 input, n output from the coaxial accessing user end
End, n is natural number；The Time Domain Reflectometry test selects an output end input test signal in the branch/distributor, selected
The waving map signal of change formula for the output end selected is：The time domain of the input
Test signal calculation formula is：
Wherein,It is the branch/distributor time domain
Test signal amplitude,It is test signal amplitude, ΔkFor the transmission range of output end to input；Reflectance factor
Calculation formula：
It is preferred that, the otdr signal of the correspondence branch/distributor is the correspondence branch/distributor and is connected
Connect at the tie point middle impedance mismatch of coaxial cable.
It is preferred that, the impedance match situation of the branch/distributor and the tie point for the coaxial cable that is connected is analyzed,
Refer to：If there is the impedance mismatch of the output end of input waving map signal in k-th of branch/distributor, correspond to
Otdr signal calculation formula is：Wherein,Reflectance factorIf the impedance mismatch of other output ends, corresponding otdr signal calculation formula is：
It is preferred that, the waving map signal of k-th of branch/distributorDelayCalculation formula is：
Wherein, vBranch/distributorFor the signal velocity in known branches/distributor；
If the impedance mismatch of k-th of branch/distributor input, its reflected signal calculation formula：
Wherein,Reflectance factor calculates formula：
It is preferred that, in addition to calculate the input and output end signal reflection loss of branch/distributor in link.
It is preferred that, the coaxial network is passive network.
As described above, the coaxial network link-quality detection method initiated based on user terminal that the present invention is provided, the side
Method is tested by initiating Time Domain Reflectometry at coaxial accessing user end, and otdr signal is received at the coaxial accessing user end,
According to the otdr signal of the corresponding coaxial cable received, head end is accessed one by one from the coaxial accessing user end to coaxial
The coaxial cable tested in the coaxial network arrives wherein one coaxial cable to judge whether to break down in test
When not breaking down and judging that the coaxial cable is connected with branch/distributor, according to the correspondence branch/distributor when
Domain reflected signal analyzes the branch/distributor with the impedance match situation of the tie point for the coaxial cable that is connected to determine link matter
Amount, this method is initiated from subscriber household end, is easy to the biography of quick investigation coaxial network link standard coaxial cable and branch/distributor
Transmission quality, it is convenient accurate, while greatly increasing broadband, television services business added value.
Brief description of the drawings
Fig. 1 is shown as an embodiment of the coaxial network link-quality detection method initiated based on user terminal of the present invention
Schematic flow sheet.
Fig. 2 is shown as coaxial network structural representation in the present invention.
When Fig. 3 is shown as the coaxial cable for the coaxial network link-quality detection method initiated based on user terminal of the present invention
Domain reflected signal model schematic.
Fig. 4 is shown as branch/distribution of the coaxial network link-quality detection method initiated based on user terminal of the present invention
Device reflected signal model schematic.
Fig. 5 is shown as the another embodiment of the coaxial network link-quality detection method initiated based on user terminal of the present invention
Link structure schematic diagram
Component label instructions
S1~S3 steps
Embodiment
Illustrate embodiments of the present invention below by way of specific instantiation, those skilled in the art can be by this specification
Disclosed content understands other advantages and effect of the present invention easily.The present invention can also pass through specific realities different in addition
The mode of applying is embodied or practiced, the various details in this specification can also based on different viewpoints with application, without departing from
Various modifications or alterations are carried out under the spirit of the present invention.
Referring to Fig. 1, the present invention provides a kind of coaxial network link-quality detection method initiated based on user terminal, it is described
Coaxial network is connected between coaxial access head end and coaxial accessing user end, and methods described includes：
Step S1：Time Domain Reflectometry test is initiated at the coaxial accessing user end；
Step S2：Otdr signal is received at the coaxial accessing user end；
Step S3：According to the otdr signal of the corresponding coaxial cable received, from the coaxial accessing user end to
The coaxial cable that coaxial access head end is tested in the coaxial network one by one is arrived with judging whether to break down in test
Wherein one coaxial cable do not break down and judge the coaxial cable be connected with branch/distributor (i.e. splitter or point
Orchestration) when, the branch/distributor and the coaxial electrical that is connected are analyzed according to the otdr signal of the correspondence branch/distributor
The impedance match situation of the tie point of cable is to determine link-quality.
As shown in Fig. 2 the coaxial network for it is passive can be such as Fig. 2 connected mode, under regular situation, the network can
To be cable TV network, cable TV signal is exactly to deliver to coaxial accessing user end from coaxial access head end；And the present invention is
Time Domain Reflectometry test is initiated at coaxial accessing user end, sense is opposite；In the present embodiment, the coaxial network is same
Shaft cable network, is Passive Coax network.Certainly active electric network is alternatively in other embodiments, not with the present embodiment
For limitation.
It should be noted that, thought principle of the invention is：When there is impedance mismatch in coaxial network link somewhere,
During coaxial user terminal transmission signal, corresponding signal will be reflected back, is analyzed from upper section, by analyzing the letter being reflected back
The delay of number power incoming signal relative with polarity and reflected signal, can just be positioned with being divided to the place of impedance mismatch
Analysis.Produce impedance mismatch the reason for, be on the one hand coaxial cable with branch/distributor because manufacturing process is existing in itself
The fluctuation of impedance, is on the one hand due to that they aoxidize impaired, loose contact generation, is also exactly that link has open circuit, short circuit
Situation.Therefore, coaxial links analysis algorithm should be able to distinguish the impedance fluctuations of coaxial cable and branch's distribution under normal circumstances
Phenomenon, with there is the difference between failure situation.Following factor is considered when designing coaxial links analysis algorithm：
A. the normal impedance fluctuation that coaxial cable is produced due to manufacturing process is negligible；The link circuit condition of coaxial cable focuses on to consider
It breaks, the situation of short circuit；B. branch/distributor, can be in a spy due to reasons such as its distinctive design structure, manufacturing process
The phenomenon of impedance fluctuations is produced in the not short time.The presence situation and orientation of branch/distributor are may determine that by the feature；
C. because signal can produce decay in coaxial cable transmission, especially reflected signal can be produced when by branch/distributor
Raw decay, therefore for the reflected signal by one or more branch/distributors, the decay of its signal should be taken into full account.
Therefore, since to do Time Domain Reflectometry test (TDR), then first carry out signal to coaxial cable, branch/distributor and build
Formwork erection type.
As shown in figure 3, the otdr signal model of display coaxial network kth bar coaxial cable, conventional at present is coaxial
Cable characteristic impedance is generally definite value, but due to reasons such as manufacturing process, there is certain fluctuation, if fluctuation is less believed that
In a normal scope, if in coaxial cable there is problem, the problem of just generating impedance mismatch in certain, it is assumed that same
The problem of shaft cable somewhere there occurs impedance mismatch, its distribution of impedance is as shown in the figure.
Therefore it is preferred that, the waving map signal of change of kth section coaxial cable initiating terminal from the coaxial accessing user end
Formula is：Wherein, the 1st section of coaxial cable from the coaxial accessing user end
Top Time Domain Reflectometry test waving map signal of change formula be：uin(0)=∫ Uin(0)(f)×ej2πftdf；Wherein, uin(0)
It is the coaxial cable waving map signal amplitude, Uin(0)(f) it is test signal amplitude, f is frequency test signal, and t is test
Time point；
Wherein, according to the measurement range L between coaxial the access head end and subscriber signal receiving terminal, test signal step is selected
Enter frequency Δ f；The Δ f is metWherein, vCoaxiallyFor the medium signal transmission speed of the known coaxial cable；
According to presumptive test precision (ΔPrecision) selected test signal cut-off frequency FCut-off, meet condition：
It is preferred that, the otdr signal of the correspondence coaxial cable is correspondence from each impedance on the coaxial cable
Place is mismatched to produce.
It is preferred that, if the resistance from the coaxial accessing user end on kth bar coaxial cable, the kth bar coaxial cable
There are j at anti-mismatch, and kth bar coaxial cable described in cutting is j+1 sections, wherein, jth section impedance is designated as zk,j；J-th of resistance
The otdr signal that anti-mismatch place is produced feeds back to the calculation formula of the kth bar coaxial cable initiating terminal：
Wherein, lk,jFor jth section
Coaxial cable length；For reflectance factor, calculation formula is：
It is preferred that, the waving map signal of the kth bar coaxial cableDelayCalculation formula is：
The output signal of the kth bar coaxial cableCalculation formula is：
It is preferred that, according to the otdr signal received, from the coaxial accessing user end to coaxial access head end by
Bar tests in the coaxial network coaxial cable to judge whether to break down, including：Set the failure include open circuit, it is short
Road；
The calculation formula of otdr signal under open circuit situation is obtained according to the otdr signal calculation formula： Obtained according to the otdr signal calculation formula under short circuit condition
The calculation formula of otdr signal：Wherein, α is signal
The attenuation coefficient transmitted in coaxial cable；Comparison receives otdr signal and it is described open a way situation under otdr signal,
Otdr signal under short circuit condition, failure (open circuit or short circuit) is judged when comparing consistent.
One of main points of the present invention, which are to increase, to be analyzed the transmission quality of branch/distributor in link, therefore, can do as
Lower judgment step：It is described to judge that the coaxial cable is connected with branch/distributor, including：Continuously received in preset time period
More than two reflected signals, and reflected signal fluctuates within the specific limits, then judges to be connected with branch/distributor.
As shown in figure 4, since it is desired that analyze the transmission quality of branch/distributor, therefore need to equally give signal modeling：Point
Branch/distributor has 1 IN input port, 1 to multiple OUT delivery outlets.
It is preferred that, if k-th of branch/distributor includes 1 input, n output end from user's receiving terminal；Institute
State Time Domain Reflectometry test the branch/distributor select an output end input test signal, selected output end when
Domain test signal of change formula is：The waving map signal of change of the input is public
Formula is：
Wherein,It is the branch/distributor time domain
Test signal amplitude,It is test signal amplitude, ΔkFor the transmission range of output end to input；Reflectance factor
Calculation formula：
It is preferred that, the otdr signal of the correspondence branch/distributor is the correspondence branch/distributor and is connected
Connect at the tie point middle impedance mismatch of coaxial cable.
It is preferred that, the branch/distributor and the impedance match situation of the tie point for the coaxial cable that is connected are analyzed, is referred to
It is：If there is the impedance mismatch of the output end of input waving map signal in k-th of branch/distributor, Time Domain Reflectometry is corresponded to
Signal of change formula is：Wherein,Reflectance factorIf the impedance mismatch of other output ends, corresponding otdr signal calculation formula is：
It is preferred that, the waving map signal of k-th of branch/distributorDelayCalculation formula is：
Wherein, vBranch/distributorFor the signal velocity in known branches/distributor；
If the impedance mismatch of k-th of branch/distributor input, its reflected signal calculation formula：
Wherein,Reflectance factor calculates formula：
It is preferred that, in addition to calculate the input and output end signal reflection loss of branch/distributor in link.
It is preferred that, the coaxial network is passive network.
Summary principle, specific testing procedure is as follows：
(1) press and TDR Test signal input is carried out in fc-specific test FC frequency range：uin(0)=∫ Uin(0)(f)×ej2πftdf；
Wherein, according to coaxial access head end and the measurement range (L) of coaxial access terminal in coaxial network to be measured, step is selected
Enter frequency Δ f：
Cut-off frequency FCut-offAccording to measuring accuracy (ΔPrecision) selection determination：
(2) reflected signal received is acquired, if signal is respectively uRef (1,0)、uRef (k, 0)、…、
uRef (k, 0)、…、uRef (n, 0), they are with input signal uin(0)Delay be respectively：tRef (1,0)、tRef (2,0)、…、tRef (k, 0)、…、
tRef (n, 0)
(3) link circuit condition of the 1st bar of coaxial cable is analyzed, and discriminates whether there is branch/distributor：
(4) open circuit and the feelings of short circuit are judged whether according to the otdr signal model of coaxial network coaxial cable
Shape, be respectively in open circuit and signal that test point is reflected back under short circuit condition：
Wherein, α is the attenuation coefficient that signal is transmitted in coaxial cable.
With reference to the two formula, judged according to the reflected signal situation received.
(5) if the problem of open circuit is with short circuit is not present in the 1st bar of coaxial cable, branch's distribution feelings of its connection are judged
Condition：If continuously received in the preset time (generally extremely short time, such as 3ns~5ns) two or more
Reflected signal, and reflected signal fluctuates within the specific limits, then judges that it is connected with branch/distributor；According to coaxial network
The model of branch/distributor, with reference to the continuous signal received, analyzes the situation of impedance fluctuations.
(6) according to coaxial cable and the otdr signal model of branch/distributor, with reference to the reflected signal of acquisition, point
The impedance match situation of kth end coaxial cable and branch/distributor is analysed, it is last until analyzing to judge coaxial links quality
One reflected signal is the whole piece link for having analyzed the user input connection for initiating test.
As shown in figure 5, following carry out calculation specifications with a specific embodiment again：
Line link matter is entered for 100 meters of coaxial network to distance range between coaxial access head end and coaxial accessing user end
Amount is assessed, and measurement accuracy is 0.5 meter.For cable television system physical-foaming polythene insulation coaxial cable, it is to signal
Spread speed vCoaxially≈0.66×3×108=1.98 × 108M/s, then it is 950KHZ to select step frequency Δ f, selects cut-off frequency FCut-off
For 100MHZ, initiate to assess into downlink quality from terminal for coaxial network as depicted and test.
Amplitude is used to send test signal for 20mV incoming signal at the t0=0 moment：
By sampling analysis, obtained larger otdr signal is as shown in the table：
By calculating, so that it may which analysis is obtained：1st article of coaxial length is 14.8m；2nd article of coaxial line length 9.39m；
2nd article coaxial line end produces open circuit；2 branch/distributors are connected between two sections of coaxial lines, diagram OUT is accessed in circuit
The reflection loss at end is about -20.8dB.
In summary, the coaxial network link-quality detection method initiated based on user terminal that the present invention is provided, the side
Method is tested by initiating Time Domain Reflectometry at coaxial accessing user end, and otdr signal is received at the coaxial accessing user end,
According to the otdr signal of the corresponding coaxial cable received, head end is accessed one by one from the coaxial accessing user end to coaxial
The coaxial cable tested in the coaxial network arrives wherein one coaxial cable to judge whether to break down in test
When not breaking down and judging that the coaxial cable is connected with branch/distributor, according to the correspondence branch/distributor when
Domain reflected signal analyzes the branch/distributor with the impedance match situation of the tie point for the coaxial cable that is connected to determine link matter
Amount, this method is initiated from subscriber household end, is easy to the biography of quick investigation coaxial network link standard coaxial cable and branch/distributor
Transmission quality, it is convenient accurate, while greatly increasing broadband, television services business added value.
Specifically, TDR e measurement technologies are namely based on, detectable signal are initiated from the user terminal of coaxial network link, then
Receive reflected signal to be analyzed, calculated according to the otdr signal model based on coaxial links and coaxial links quality analysis
Method, whether there is to obtain in the coaxial links quality from coaxial accessing user end to head end, including assessment coaxial network link
Branch/distributor, branch/distributor reflection loss situation, and with the presence or absence of open circuit, open circuit etc..Due to being from user terminal master
It is dynamic to initiate to detect into downlink quality, so this method is highly suitable for applying when EoC, C-DOCSIS user's opening link：By
The O＆M engineer of operator is quick to check in user family to having between EoC, C-DOCSIS headend when on-siteing install
Line coaxial links quality, hidden danger of fixing a breakdown improves user and taken up rate.
The above-described embodiments merely illustrate the principles and effects of the present invention, not for the limitation present invention.It is any ripe
Know the personage of this technology all can carry out modifications and changes under the spirit and scope without prejudice to the present invention to above-described embodiment.Cause
This, those of ordinary skill in the art is complete without departing from disclosed spirit and institute under technological thought such as
Into all equivalent modifications or change, should by the present invention claim be covered.
Claims (8)
1. a kind of coaxial network link-quality detection method initiated based on user terminal, the coaxial network is connected to coaxial access
Between head end and coaxial accessing user end, it is characterised in that methods described includes：
Time Domain Reflectometry test is initiated at the coaxial accessing user end；
Otdr signal is received at the coaxial accessing user end；
According to the otdr signal of the corresponding coaxial cable received, from the coaxial accessing user end to coaxial access head end
The coaxial cable tested one by one in the coaxial network is continuously received with judging whether to break down in preset time period
To more than two reflected signals, and reflected signal is fluctuated within the specific limits, then judges to be connected with branch/distributor, if
When testing wherein one coaxial cable and not breaking down and judge that the coaxial cable is connected with branch/distributor, according to
The otdr signal of the correspondence branch/distributor analyzes the branch/distributor and the tie point for the coaxial cable that is connected
Impedance match situation is to determine link-quality；
Wherein, the coaxial cable tested one by one in the coaxial network to coaxial access head end from the coaxial accessing user end with
Judge whether to break down, including：
The waving map signal of change formula of kth section coaxial cable initiating terminal is from the coaxial accessing user end：Wherein, the 1st section of coaxial cable initiating terminal from the coaxial accessing user end when
The waving map signal of change formula of domain reflection measurement is：uin(0)=∫ Uin(0)(f)×ej2πftdf；Wherein, uin(0)It is described same
Shaft cable waving map signal amplitude, Uin(0)(f) it is test signal amplitude, f is frequency test signal, and t is testing time point；Its
In, according to the measurement range L between the coaxial access head end and coaxial accessing user end, select test signal step frequency Δ
f；The Δ f is metWherein, vCoaxiallyFor the medium signal transmission speed of the known coaxial cable；According to predetermined
Measuring accuracy ΔPrecisionSelected test signal cut-off frequency FCut-off, meet condition：It is described correspondence coaxial cable when
Domain reflected signal is correspondence from being produced on the coaxial cable at each impedance mismatch；
If having at the impedance mismatch on the kth bar coaxial cable from the coaxial accessing user end, the kth bar coaxial cable
J, and kth bar coaxial cable described in cutting is j+1 sections, wherein, jth section impedance is designated as zk,j；J-th of impedance mismatch place
The otdr signal of generation feeds back to the calculation formula of the kth bar coaxial cable initiating terminal：
Wherein, lk,jFor jth section coaxial cable length；For reflectance factor, calculation formula is：
Setting the failure includes open circuit, short circuit；Time domain under open circuit situation is obtained according to the otdr signal calculation formula
The calculation formula of reflected signal：According to the otdr signal meter
Calculate the calculation formula that formula obtains otdr signal under short circuit condition： Wherein, α is the attenuation coefficient that signal is transmitted in coaxial cable；Comparison receives otdr signal and opened with described
Otdr signal under otdr signal, short circuit condition under the situation of road, failure is judged when comparing consistent.
2. the coaxial network link-quality detection method according to claim 1 initiated based on user terminal, it is characterised in that
The waving map signal of the kth bar coaxial cableDelayCalculation formula is：
The output signal of the kth bar coaxial cableCalculation formula is：
3. the coaxial network link-quality detection method according to claim 1 initiated based on user terminal, it is characterised in that
If k-th of branch/distributor includes 1 input from user's receiving terminal, n output end, n is natural number；When described
Domain reflection measurement selects an output end input test signal in the branch/distributor, and the time domain of selected output end is surveyed
Trial signal calculation formula is：The waving map signal of change formula of the input is：
Wherein,It is the branch/distributor waving map signal amplitude,It is test signal amplitude, ΔkTo be defeated
Go out end to the transmission range of input；Reflectance factorCalculation formula：
4. the coaxial network link-quality detection method according to claim 3 initiated based on user terminal, it is characterised in that
The otdr signal of the correspondence branch/distributor, is the connection of the correspondence branch/distributor and institute's connecting coaxial cable
At point middle impedance mismatch.
5. the coaxial network link-quality detection method according to claim 4 initiated based on user terminal, it is characterised in that
The impedance match situation of the branch/distributor and the tie point for the coaxial cable that is connected is analyzed, is referred to：
If there is the impedance mismatch of the output end of input waving map signal in k-th of branch/distributor, Time Domain Reflectometry is corresponded to
Signal of change formula is：
Wherein,Reflectance factor
If the impedance mismatch of other output ends, corresponding otdr signal calculation formula is：
For input reflectance factor.
6. the coaxial network link-quality detection method according to claim 5 initiated based on user terminal, it is characterised in that
The waving map signal of k-th of branch/distributorDelayCalculation formula is：
vBranch/distributorFor the signal velocity in known branches/distributor；
If the impedance mismatch of k-th of branch/distributor input, its reflected signal calculation formula：
Wherein,Reflectance factor calculates formula：
7. the coaxial network link-quality detection method according to claim 3 initiated based on user terminal, it is characterised in that
Also include the input and output end signal reflection loss for calculating branch/distributor in link.
8. the coaxial network link-quality detection method according to claim 1 initiated based on user terminal, it is characterised in that
The coaxial network is passive network.
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