CN102916743B - The method of the asymmetric difference accurate measurement of a kind of time delay - Google Patents

Abstract

The invention discloses the method for the asymmetric difference accurate measurement of a kind of time delay, the method of accurately measuring for asymmetric difference carries out analyzing and proposing solution, this solution does not increase extra precision measuring instrument instruments and meters, by means of only HTF-BITS(split-second precision frequency BITS equipment) adopt regular two-way three-dimensional time coordinate alignment algorithm, the automatic equalization of carrying out the automatic comparison of data link, automatic calibration and asymmetric difference compensates.Integration three grades of synchronizing networks that the national super high precision achieved, superhigh precision, split-second precision frequency (≤± 1ns ,≤± 10ns ,≤± 20ns) merge.By the popularization of the method, it's 200,000,000 years toing 1 second for the super high precision Time and frequency standard can be delivered under the sun by ground (underground) optical-fiber network, for various types of communication network provides required super high precision time reference.

Description

The method of the asymmetric difference accurate measurement of a kind of time delay

Technical field

The invention belongs to optical communication transmission network network field, relate to the method for the asymmetric difference accurate measurement of time delay in a kind of optical communication transmission network network.

Background technology

It net refers to that the temporal frequency synchro system (being called for short sky net) in day space comprises two large classes: a class is GPS, GLONAIS, the Big Dipper and galileo satellite navigation system.In general equator adds several quiet getting on the right track and add that 33, the whole world of high-speed cruising just constitutes sky satellite navigation temporal frequency Synchronization Network.To the year two thousand twenty GPS three generations time service precision≤1ns; Positioning precision≤0.2 ~ 0.5 meter;

Another kind of is ACES(space atomic clock group).ACES comes into effect to be transmitted into satellite atomic clock group of future generation on international space station AIPHA for 2003, is by the U.S., Russia, Japan, Europe and a high frequency stability of Canadian Joint Implementation and the cesium-beam atomic clock of high accuracy or hydrogen atomic clock.Timing experiment room, high performance space is set up at AIPHA station.ACES is an important temporal frequency research platform, if ground atomic clock and it compare, comparison accuracy two orders of magnitude higher than GPS.The development of ACES atomic clock technology is beneficial to the development of follow-on Global Navigation Satellite System (GNSS).

It net temporal frequency precision is very high, the whole world Anywhere any time the receiver of any reception sky temporal frequency net Satellite than being easier to be better than the time service precision of GPS and frequency stability and accuracy (1 grade of clock level).

But sky net also has a lot of shortcoming simultaneously.Its maximum shortcoming is unsteadiness: the interference being subject to atmospheric environment, the pulse of sun nuclear-magnetism etc. on the one hand; On the other hand artificial disturbance or artificial close interrupt or war smash damage, antenna feeding system must be had to collect mail breath from air interface could normal work in addition.

Earth mat: China is just building up the underground optical communication transmission network network of Eight Verticals and Eight Horizontals has at the end of last century been form by three large telecommunications operating company and national defence private network, power communication private network etc. the underground communication net extended in all direction now.Therefore underground is that supporting body is set up temporal frequency Synchronization Network and is called earth mat by optical communication transmission network network by we.

Not relying on GPS Big Dipper sky satellite navigation system to transmit and the core in the synchronous split-second precision source of slave station to realize underground optical communication transmission system, is accurately measure technology to the propagation delay time of optical transmission communication network and asymmetric difference thereof.

The current use split-second precision measuring instrument of being correlated with can measure to optical communication transmission system time delay the once benefit that certain precision and right title difference carry out passive type and taste.Due to optical communication transmission network network aspect, facts have proved that the propagation delay time of optical transmission communication network and asymmetric difference thereof are the numbers of a change at random, that is must regularly carry out measuring and correcting.

In optical communication transmission network network, apply two-way time code stream correlation technique to the reliable and stable operation of whole network, detect the marginal performance of whole network in advance, send marginal performance alarm, thus ensure the low interruption rate of communication network.

Summary of the invention

The object of the invention is integration three grades of synchronizing networks of the national super high precision of establishment (≤± 1ns ,≤± 10ns ,≤± 20ns), superhigh precision, the fusion of split-second precision frequency.By the popularization of the method, it's 200,000,000 years toing 1 second for the super high precision Time and frequency standard can be delivered under the sun by ground (underground) optical-fiber network, for various types of communication network provides required super high precision time reference.

The object of the invention is to solve by the following technical programs:

The method of the asymmetric difference accurate measurement of a kind of time delay:

1) in split-second precision frequency BITS equipment, set up optical communication transmission network network, lead-stand by optical communication transmission network network passing time reference signal between synchronizer, main website and slave station time synchronized adopt two-way pumping station mode;

2) time interval deviation of following calculated with mathematical model MS master-slave synchronizer is adopted:

In 1. formula, Es represents principal and subordinate's relative time-intervals deviation;

E0 represents principal and subordinate's initial interval deviation;

represent the remaining time drift error of principal and subordinate's Frequency Synchronization after application frequency and phase discrimination zero passage detection Phase Lock Technique;

Δ T _xyt () represents asymmetric difference, i.e. Δ T _xy(t)=| T _x(t)-T _y(t) |, wherein T _xt () represents the time interval value of signal between optical communication transmission network network to slave station clock synchronization device signal sent by master clock synchronizer, T _yt () represents the time interval value of signal between optical communication transmission network network to master clock synchronizer Received signal strength that slave station clock synchronization device sends;

represent the randomized jitter noise that optical-fiber network is introduced when passing time benchmark;

1. in formula, first three items is completed by long-distance remote control loose coupling frequency and phase discrimination zero passage detection Phase Lock Technique, and control errors is at ± 5X10 ^-14/ sky;

3) three-dimensional time coordinate is adopted to accurately measure Δ T _xyt (): in main website, measure loopback cycle C value, loopback cycle C value is: C=T _xi(t)+T _yit (), i represents bit quantity, chooses nominal period C according to C values different in table 1 _markvalue,

Table 1

Loopback cycle C

<125us

<250us

<1ms

...

<10ms

<100ms

...

Nominal period C Mark

125us

250us

1ms

...

10ms

100ms

...

Work as T _xi(t)=T _yi(t), △ T _xiyiduring (t) ≈ 0, realize master station and follow station two-way pumping station and transmit equal with the propagation delay time of back;

Work as T _xi(t) > T _yitime (t),

Work as T _xi(t) < T _yitime (t),

By △ T _xiyit () precisely measures, realize MS master-slave relative time synchronous;

Further above-mentioned employing two-way pumping station mode is two-way time code stream comparison;

Realizing the synchronous precision of MS master-slave relative time is further≤± 20ns ,≤± 10ns ,≤± 5ns ,≤± 2ns or≤± 1ns; The low phase noise platform of further employing split-second precision frequency BITS equipment, makes to measure precision and improves doubly, wherein N represents the number of times of duplicate measurements in 1 second, the time of τ observation test.

The present invention is directed to asymmetric difference △ T _xyt the method for accurately measuring of () carries out analyzing and proposing solution, this solution does not increase extra precision measuring instrument instruments and meters, by means of only HTF-BITS(split-second precision frequency BITS equipment) adopt regular two-way three-dimensional time coordinate alignment algorithm, the automatic equalization of carrying out the automatic comparison of data link, automatic calibration and asymmetric difference compensates.

Accompanying drawing explanation

Fig. 1 a-1b is three-dimensional coordinate C _mark=1ms instrumentation plan;

Fig. 2 is 1000km two-way timing code flow data link comparison schematic diagram;

Fig. 3 is the schematic diagram for Chengdu.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail:

The method of the asymmetric difference accurate measurement of a kind of time delay:

1) in split-second precision frequency BITS equipment, set up optical communication transmission network network, lead-stand by optical communication transmission network network passing time reference signal between synchronizer, main website and slave station time synchronized adopt two-way pumping station mode;

2) time interval deviation of following calculated with mathematical model MS master-slave synchronizer is adopted:

In 1. formula, Es represents principal and subordinate's relative time-intervals deviation;

E0 represents principal and subordinate's initial interval deviation;

represent the remaining time drift error of principal and subordinate's Frequency Synchronization after application frequency and phase discrimination zero passage detection Phase Lock Technique;

Δ T _xyt () represents asymmetric difference, i.e. Δ T _xy(t)=| T _x(t)-T _y(t) |, wherein T _xt () represents the time interval value of signal between optical communication transmission network network to slave station clock synchronization device signal sent by master clock synchronizer, T _yt () represents the time interval value of signal between optical communication transmission network network to master clock synchronizer Received signal strength that slave station clock synchronization device sends;

represent the randomized jitter noise that optical-fiber network is introduced when passing time benchmark;

1. in formula, first three items is completed by long-distance remote control loose coupling frequency and phase discrimination zero passage detection Phase Lock Technique, and control errors is at ± 5X10 ^-14/ sky;

Three-dimensional time coordinate accurately measures T _xi(t), T _yi(t), and principle.

In the comparison of two-way timing code flow data

C=T _xi(t)+T _yi(t)②

Main website (MASTER) loopback C value measurement as shown in Figure 1 a, 1 b.

In a pair Optical Fiber Transmission, Frequency Synchronization is better than 1X10 ^-11level, works as F _main=F _from, namely the time interval measurement at two ends is identical.

C _{ring master}=C _{ring from}=T _xi(t)+T _yit () 3.

According to IEEE1588one-step principle at main website code stream output panel of two-way time with main website 1PPS initial point and 1PPS rising edge for starting point, send T to slave station _xit () remote measurement time interval code stream realizes two-way contrast.

C is chosen according to different loopback C value _markvalue, as shown in table 1:

Table 1:C _markvalue and loopback C value convert

C _markcycle frequency time code stream is exactly the nominal time interval code stream that main website sends, and its effect has: (with C<1ms, C _mark=1ms, 50Km optical communication is end-to-end is example)

Use C _mark=1ms, namely by main website (MASTER) 1PPS initial point with some rising edge alignment after (error≤1ns, and define the 1000PPS initial point of the decile of 1,000 1000PPS, and with this 1000PPS initial point for starting point, sending to slave station (SLAVER).

MS master-slave station optical transport postpones Txi (t), the average delay value of 1 second

$T_{\mathrm{xi}}\left(\stackrel{\&OverBar;}{t}\right)=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{T}_{\mathrm{xi}}\left(t\right)/N$

From-main website optical transport length of delay Tyi (t), the average delay value in 1 second

$T_{\mathrm{yi}}\left(\stackrel{\&OverBar;}{t}\right)=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{T}_{\mathrm{yi}}\left(t\right)/N$

The normalizing time interval code stream standard average being sent to slave station by main website in 1 second wherein, N is determined by the distance length at optical communication transmission network MS master-slave station.

T _xithe definition of (t) to be main website 1PPS rising edge of a pulse be starting point to the regeneration UTC1PPS rising edge of a pulse of slave station be a little between time interval difference, it is the end-to-end propagation delay time value at MS master-slave two ends.At C _markt in cycle _xit () only occurs once cycle is judgement T _xi(t) >T _yi(t) or T _xi(t) <T _yidimension one coordinate of (t).C _markcycle namely the time interval, then correspondence led bit frequency is with the starting point of the 1PPS rising edge alignment of main website (can be with frame head or not be with frame head).Namely this leads complete " 1 " code that bit frequency is 1KHz, and namely main website is toward the 1MS standard time interval code stream of downstream broadcast.T _xi(t), with only occur once within the 1ms cycle, do not have second pulse and occur.Although this rising edge can be introduced randomized jitter may be very large, but the retest having 10-8000 time per second, obviously will increase many times than the direct comparison precision of two station 1PPS, thus effectively filtering randomized jitter value.

Survey accurate T _xit modulation /demodulation error all equilibrium in Time Transmission can compensate by the meaning of () value in SDH and other optical communication transmission network network, be continuous continual characteristic to keep the feature of TID<1ns time interval code stream.From time reference 1PPS+TOD, 1PPS, E1+1PPS, E1+DCLS etc. that main website sends to oneself synchronous all slave station.

Be that starting point (band timestamp frame head) arrives slave station after optical communication transmission network bearer network in main website with master clock regeneration UTC atomic time (synchronously more high-grade after) time reference 1PPS initial point, from clock will set up from clock regeneration UTC atomic time time reference point 1PPS _frominitial point place demodulates this point.

T ₂=1PPS _frominitial point+T _xit () be i.e. t ₂-t ₁=T _xi(t)

Loopback measures C value: C=T _xi(t)+T _yi(t)

In main website, from main website by regenerating UTC atomic time time reference 1PPS initial point, send this value of cycle is not integer, relies on synchronization frequency division to be irrealizable, and adopts DDS technology to realize, but the clutter interference introduced is then introduce error TID level to increase phenomenon.And adopt the time interval code stream of frequency, through slave station carry out two-way pumping station.

Regeneration UTC atomic time split-second precision Frequency Synchronization net is exactly the technology of graduation transmission and purification temporal frequency precision.Utilize high accuracy Frequency Synchronization technology by within 200,000,000 years, differ from one second atomic clock oscillator be better than 1X10 ^-15stability be graduately delivered to the level Four Synchronization Network node be made up of HTF-BITS equipment:

Caesium≤± 5X10 ^-14/ sky, rubidium≤± 5X10 ^-14/ sky, X ₀₁≤ ± 1X10 ^-13/ sky, X _o2≤ ± 5X10 ^-13/ sky, X _o3≤ ± 1X10 ^-12/ sky.

Due to the particularity of this physical quantity of time, it must be continuously continual, if create phase jumping in transmittance process, frequency kick, in the TID of actual measurement (time interval deviation), just there is kick to occur, serious just likely now lose second or jump second generation.And time step is an event that cannot reverse recovery.The transmission of obvious super high precision time reference, the rule of the transmission particularly in fiber medium must be perfectly clear.If minimum for the damage of the super high precision time reference of main website is delivered to slave station, this is only the essence of Time Transmission.

The Frequency Synchronization that the present invention adopts is by the frequency relative bias≤± 5X10-of the frequency of main website and slave station ¹⁴/ sky.Relative phase deviation PD≤± 2ns/ days≤± 5ns/ days≤± 20ns/ days, wherein, the MS master-slave frequency and phase discrimination zero passage detection Phase Lock Technique of 8KHz.For successfully completing slave station and (be generally X from clock ₀) " flex point " follow the tracks of master lock due to master clock (such as caesium clock, rubidium clock) " zero point ", here " flex point " and " zero point " is zero passage detection Phase-Locked Synchronous technology specific term, tell on the one hand we from " flex point " of station clock be after slave station enters the steady track stage of loose coupling ideal second order loop with master clock comparison ± MX10 at zero point ^-N/ sky, change point, that is, when the control word that we control clock changed for ± (1 ~ 2) bit in certain moment, fundamental frequency accuracy is positive and negative two the corresponding swing points from clock highest stabilizing, it is the same that mirror image due to pendulum swings zero crossing, Here it is eliminates the Optimal Control technology of drifting about, on the other hand, " zero point " of master clock is exactly " flex point " of its synchronous more high-grade master clock " zero point ", flex point and zero point are corresponding, and the difference also with place node location in Synchronization Network changes.That is, " zero point " and the flex point of various grade are all relative, and the flex point of caesium clock is the regeneration UTC atomic time temporal frequency " zero point " after it and national time service center " zero point " synchronizing comparison.The rest may be inferred, the node of composition level Four split-second precision Frequency Synchronization net.

The 8000PPS-1000PPS-100PPS-10PPS-1PPS series that (with the UTC1PPS initial point) that produced by master clock is formed for benchmark synchronization of time intenals code stream realizes two-way transmission transmission and reception in a fiber, and realizes two-way pumping station, synchronous technology.The principle of two-way for TimeTechTWSTFT satellite temporal frequency comparison and portion of techniques are used for carrying out Time Transmission in optical fiber communication transmission system, receive.Design a kind of special optic fibre optical communication time interval code stream based on FPGA to transmit and receiving chip (<1ns).

The key element of precise synchronization:

(1) because Frequency Synchronization is to time delay too much requirement, thus high-precision Frequency Synchronization complete by formula 1. in first three items control errors at 5X10 ^-14/ sky and in PD< ± 1ns/ days.

(2) HTF-BITS equipment low phase noise platform thus ensure that what (10-10000 second) in a short time can realize from station clock duplicate measurements, will measure precision and improve doubly, N is the number of times of duplicate measurements in 1 second; τ is the time (unit second) of observation test, according to the clock of different stage, can be 10-10000 second or longer, can select, make according to specific requirement (shake of 3-5us) filtering, this just makes three the key index FD≤± 5X10 of the UTC atomic time Time and frequency standard of slave station clock regeneration ^-14/ sky, PD≤± 2ns, TID≤± 1ns.

There is certain length of delay from master clock equipment elapsed time benchmark output unit to optical transmission device interface, also there is a very little length of delay in light E/O optical fiber of making a start.Main website E/O interface is the transmission delay value of optical fiber to slave station E/O interface, this value generally engineering opening starting stage equal people for compensating to Txi (t)=Tyi (t).Fiber optical communications receiving equipment outputs to temporal frequency equipment input port and also there is certain length of delay.

The propagation delay time asymmetry change of optical fiber is main.Also prove in practice, the propagation delay time of optical fiber, with external environment and the reason such as aging thereof, changes for a long time in time, instead of a definite value.It is far from being enough for only relying on the passive type carrying out asymmetric difference during engineering opening to compensate.Therefore the Changing Pattern measured adopts front end fiber optic network automatic equalization to compensate.

Advantage:

(1) balanced asymmetric difference makes T _xi(t)=T _yi(t), △ T _xiyi(t) ≈ 0.

(2) reduce simultaneously or increase the one direction drift value due to reason introducings such as temperature, remaining the normalizing (C of A → B or B → A _mark) time delay value remains unchanged for a long period of time.Guarantee the identical of bidirectional service data link channel, and the intelligent locking that long term maintenance steady state value is constant.

(3) T is changed _xit namely () value changes the slope of MS master-slave coordinate and the scope be split into as Fig. 1 a, Fig. 1 b interior change back and forth.For accurately determining put and find accurately specular point is significant.

(4) from A → B → C →...→ N step by step equalizing fiber compensate guarantee 2000Km(or 1000Km) direct route of distance, the transmission line time delay value namely between two big cities △ T _xiyit ()≤± 1ns or (± 5ns) technically, are of great immediate significance economically.Also can 1000Km, direct route between two big cities, final slave station (slave station of cesium-beam atomic clock or rubidium atomic clock composition) carrys out isostatic compensation.Front end optical-fiber time-delay automatic equalization phase-locking compensation and rear end electricity mouth, based on the time-delay network of FPGA composition, the electric mouth time interval delay equalization phase-locking compensation of composition.The balanced phase-locking compensation of electricity mouth is deadline Frequency Synchronization between primary HTF-BITS in MS master-slave station and the HTF-BITS of slave station, and carries out two-way time interval bit stream data link list and complete without interior, does not change T _xi(t) ≠ T _yithe out and out situation of (t), the in esse actual state T of the transmission line namely between MS master-slave station _xi(t) ≠ T _yit () asymmetrical state still exists.Bidirectional service data code stream passage is still asymmetric, and only has on two-way time interval bit stream data comparison passage and complete

Work as T _xi(t) > T _yitime (t),

Work as T _xi(t) < T _yitime (t)

Specular principle is utilized to utilize 8000PPS-1000PPS-100PPS in a word in FPGA design, main website is synchronized with 1PPS 125us cycle ~ the 10ms cycle criterion time interval is delivered to the realization of slave station, and the realization of two frequency and phase discrimination zero passage detection above, will randomized jitter noise filtering.By △ T _xiyit () precisely measures, realize the synchronous Jing Du≤1ns of MS master-slave relative time.

The time delay value T of optical fiber _xi(t), T _yit accurately measuring of () also has other measures (instrumentation) to accurately measure out in engineering construction.Returned by electric choma again and measure C value, its error be two ends optical terminus machine equipment electricity mouth time delay value (although this value is very little, by light-electricity, electrical-optical conversion generation.C=T _xi(t)+T _xi(t)+T _{equipment sends}(t)+T _{equipment receives}(t)

Wherein, T _{equipment sends}(t), T _{equipment receives}t () generally value should be very little, and asymmetric difference is less, and the equipment for different manufacturers may slightly difference, should say employing calculate the propagation delay time with correction-compensation terminal equipment, in super high precision time synchronized or in superhigh precision time synchronized, give correction-compensation, make T _{equipment sends}(t)=T _{equipment receives}t () is also easy to realize.Thus, when engineering opening, optical fiber T is precisely measured _xi(t), T _yit (), makes the asymmetric Cha Zhi≤1ns of the propagation delay time at MS master-slave two ends neither difficult matter, this method also can press three-dimensional coordinate algorithm at MS master-slave two ends, makes the 1PPS initial point of main website and slave station, relative time-intervals Wu Cha≤1ns.

The super high precision time interval deviation of long-term Wei Chi≤1ns, sets up Synchronization Network group net principle and the method for reliable and stable level Four Time and frequency standard.

Embodiment 1:

Experiment lab simulation 50km optical transport network, frequency and phase discrimination zero passage is resurveyed remote control " loose coupling " frequency of phase locking simultaneous techniques 10mhz low phase noise output system platform, asymmetric difference, the balanced phase-locking compensation of three-dimensional time coordinate remote measuring and controlling loose coupling, experimental result: Frequency Synchronization: ± 5x10 ^-14/ sky, time synchronized: < ± 20ns/ days.

The cesium-beam atomic clock of (the comprising the private network of configuration Cs atom) of three Cs atom at the national communication network center in underground optical communication transmission system and drug in some provinces and national time service center (Shaanxi Observatory) with time service center for main website.Set up the key Synchronization Network in China's super high precision temporal frequency whole nation, complete high-quality atomic clock and (be better than 1x10 ^-15/ sky) synchronous with principal and subordinate's temporal frequency of technical grade cesium-beam atomic clock, super high precision.As shown in Figure 2, main website: Shaanxi Observatory, time service central laboratory of country is embedded with two-way timing code flow data link and sends the unit that output unit and the asymmetric difference of reception three-dimensional time coordinate remote measuring and controlling " loose coupling " the balanced phase-locking compensation propagation delay time that also embedded by the slave station cesium-beam atomic clock outside 1000km claim, and returns main website and realize two-way timing code fluxion accordingly to unit.

The precision of temporal frequency is better than 1x10 ^-15~ 1x10 ^-16level (or higher), that is master clock (Shaanxi time) is at least higher than technical grade caesium clock 2 to 3 orders of magnitude.

Main website T _xi(t)+T _yi(t)=C _i(t) or slave station T _xi(t)+T _yi(t)=C _i(t)

Select C _mark> C _it () value, the 1000km optical fiber one way propagation delay time of 1550.12 wavelength is about 4897619.5ns, i.e. about 4.897ms.I.e. C _it () <10ms, so C _mark=10ms; C _mark-C _i(t)=20.4761us.

T from main website to slave station _xit () and slave station are to the T of main website _yit the value of () is objectively that the instantaneous value in any moment is all definitely unequal.That is, the asymmetric difference of propagation delay time is absolute being.

Two passages equal is relative, temporary transient, wants to make the changing value regularly must measuring it carries out phase-locked isostatic compensation correction.

Set up following three-dimensional time coordinate:

Be that the clock that same a starting point is sent to slave station (has completed Frequency Synchronization ± 5x10 by introduction above from the 1pps of main website main initial point time reference point ^-14more than/sky), be that the regular two-way pumping station of main high-speed and high-efficiency realizes relative remote measuring and controlling " loose coupling " Phase-Locked Synchronous from the three-dimensional time coordinate that main website sends with this low noise (<1ns) of the Low phase noise sound output system from station clock with me.Set up relative time precision to be better than ± basis of the slave station time base station of 2ns is precisely measured with mean value or root mean square balanced phase-locking compensation correction, set up the relative time-offsets (if measurement <1ns) of 1pps from initial point of slave station:

here the backbone node of key Synchronization Network and the relative Long-term waved at national time service center is referred to.Certainly be better than ± prerequisite of 2ns be the scale of measurement in the time interval is be better than 1ns.Background phase noise and the reverse isolation degree of the low phase noise system of principal and subordinate are respectively:

Phase noise (10MHZ radio frequency)

1Hz	-115dBc/Hz~-125dBc/Hz
		10Hz	-135dBc/Hz~-145dBc/Hz
100Hz	-145dBc/Hz~-155dBc/Hz
		1KHz	-155dBc/Hz~-160dBc/Hz
10KHz	Below-165dBc/Hz(is background and makes an uproar mutually-165dBc/Hz)

Reverse isolation attenuation is better than 125dB, and rubidium clock and crystal clock will relax.The object setting up low phase noise platform be guarantee clock (refer to 10s ~ 10000s) in a short time between jittering noise and the time interval of time shake be better than 1ns.

Embodiment 2:

Level Four temporal frequency Synchronization Network is relied on to form national split-second precision Frequency Synchronization net.By national time service center with there is each specialized communication industry that three cesium-beam atomic clocks (hydrogen atomic clock) form (as China Mobile, CHINAUNICOM, national defence time service center ... .) etc. national (the 0 grade of super high precision Time and frequency standard frequency≤± 5X10 of composition ^-15/ sky time≤± 1ns/ days ,≤± 5X10- ¹⁵/ 7 days time≤± 1ns/7 days ,≤± 5X10 ^-15/ year≤± 1ns/.

1) from the superfine backbone network of automatically tracing to the source at national time service central master station-national communication center, realize frequency by more than three direct routes and realize frequency and phase discrimination " zero passage " detection, remote control " loose coupling " is phase-locked traces to the source automatically, makes frequency≤± 5X10 ^-15/ sky, then by the bit stream data chain comparison of the direct route two-way time interval, find out regular interior (1 day or 7 days) because the Changing Pattern of optical transport network propagation delay time, the △ T both produced _xit _yit the situation of change of (), slave station adopts front end optical-fiber time-delay automatic equalization correction-compensation phase-locked, makes T _xi(t)=T _yi(t)

Here frequency discrimination refers to C _markthe frequency in cycle

Comparison 8000PPS-10PPPS-1PPS, to relative time interval error≤± 1ns/ days (or≤± 2ns/ days) beginning to the 1PPS initial point making slave station construction stand eventually and main website.Because the change of time does not affect frequency-synchronization reference, time delay is only that the time delay value of the transmission channel of optical transmission communication network there occurs the asymmetric difference change increasing or reduce or draw, this can not lean on frequency-synchronization reference frequency shift or phase change to realize, and must keep slave station-main website between the two by optical fiber automatic equalization from end front end this nominal definite value realizes (or in slave station rear end by electric mouth, namely realizing in the bit stream data comparison of the slave station two-way time interval after opto-electronic conversion) an important link is that all time data code streams transmission of the UTC atomic time of slave station clock regeneration returns object and the meaning that main website carries out time check, i.e. steady track " loose coupling " Phase Lock Technique in two-way time interval bit stream data comparison.

At national time service center and every profession and trade optical transmission communication network center, embed HTF-BITS split-second precision Frequency Synchronization two-way time interval data code stream contrast unit, change after national super high precision backbone network (hundreds of kilometer ~ several thousand kilometer) distance realizes " loose coupling " frequency and phase discrimination zero passage detection, adopts two-way slave station to return main website and checks that verification unit has plurality of advantages:

Periodic check main website (both national time service center) knows relative frequency deviation and the phase deviation of the clock of the node that it is synchronous very accurately.

Main website can measure the relative time-intervals deviation between its product of each slave node 1PPS backtrack test accurately.

Main website can detect whether slave station regeneration UTC atomic time time message has error code generation jump second to lose second and bit error probability is much accurately automatically.

If slave station clock setting limit performance alarm, reports main website by the operating state from station clock.So whether main website just can be arrived marginal state to each by the clock of synchronous slave node and send early warning instruction, keeps stability, the reliability of super high precision temporal frequency Synchronization Network.Realize the low interruption rate of the whole network.The super high precision Time and frequency standard being delivered to national each communication hub by national time service center like this maintains long-term reliable and stable work.

2) the superhigh precision Frequency Synchronization of automatically tracing to the source at national communication hub-all provinces, municipalities and autonomous regions center.

Communication center, the whole nation refers to China Mobile, China Telecom, CHINAUNICOM, national defence communication network, powerline network center .... etc., they are by jointly setting up superfine backbone network with national time service center.Have three atomic clocks national communication center (comprising alternative communication center), and have and receive air navigation satellite system (Big Dipper, GPS etc.) Time and frequency standard, and participate in " sky net " namely in-flight time frequency Frequency Synchronization net.The star atomic clock detection check comparison work of single satellite, the state that can be the controlled radical clock in the satellite in China's Beidou satellite navigation system provides timing unsteadiness, auxiliary national time service center.。Deng, the change in long term of checking Big Dipper temporal frequency Synchronization Network and the super thresholding situation of control system.

The Main Function of each message center is then provide regeneration UTC atomic clock time-frequency relative datum (i.e. so-called master clock " zero point ") and national time service center comparison relative frequency Zhun Que Du≤± 5X10 in the communication network area administered separately for them ^-15/ sky, Xiang biased Cha≤± 1ns/ days, relative time-intervals Pian Cha≤± 1ns/ days.

As the technical indicator standard of main website " zero point ", set up the regeneration UTC atomic time Time and frequency standard of respective communication network, be all provinces, municipalities and autonomous regions' communication network management center, temporal frequency " zero point " is provided.Synchronizer configuration rubidium atomic clock (Rb) some provinces and cities' center configuration of (or claiming first nodes benchmark) general provinces and cities message center has cesium-beam atomic clock.Form the national one-level Backbone Communication network of every profession and trade communication network.In each province, intown synchronizer generally remains with the object of GPS/ Beidou satellite navigation temporal frequency sync identification receiving element and is many one and synchronously joins just input channel by " sky net " temporal frequency.Add three ground direct routes " earth mat " and with realize temporal frequency to few two adjacent provinces, cities and autonomous regions and detect, to verify the long base stability of self, the method of such 1 grade of node verification objectively judges the timing unsteadiness of all transmission line timing labile states of the people and node, and that what is called " third party " comparison technology adopts this measure to ensure that the stability of the superhigh precision temporal frequency of optical transport network and low interruption rate.

As shown in Figure 3 for the schematic diagram in Chengdu.

By above measure, HTF-BITS Equipments Setting rubidium clock realizes the relative frequency Pian Cha≤± 5X10 with main website (national communications network center) ^-14/ sky, relative phase Pian Cha≤± 2ns/ days relative time-intervals Pian Cha≤± 2ns/ days.

And take this technical indicator as the prefecture-level communication center node Time and frequency standard (with provinces, cities and autonomous regions' message center comparison) when producing secondary regenerator UTC that desynchronizes regeneration UTC atomic time of " zero point " Time and frequency standard of the key Synchronization Network of secondary within the scope of provinces, cities and autonomous regions.Relative frequency Pian Cha≤± 1X10 ^-13/ sky, relative phase Pian Cha≤± 5ns/ days, relative time-intervals Pian Cha≤± 5ns/ days.

The communications industry such as the China Mobile that condition is good all configures rubidium clock, generally the configurable highly stable crystal clock Xo that is enhanced to: three grades of nodes should be counties and districts' message center.Counties and districts level HTF-BITS, the reinforced Xo of a general configuration ₁or its standard of its regeneration of plain edition Xo UTC atomic time temporal frequency is the relative frequency Pian Cha≤± 2.3X10 of master clock ^-13/ sky, relative phase Pian Cha≤± 10ns/ days, relative time-intervals Pian Cha≤± 10ns/ days.

Level Four node is base station and community, small towns HTF-BITS, generally with Xo ₂and Xo ₃(the cheap crystal clock of single constant temperature low phase noise is from clock.The UTC atomic time Time and frequency standard of regeneration and main website comparison relative frequency Pian Cha≤± 5X10 ^-13/ sky, relative phase Pian Cha≤± 20ns/ days, relative time-intervals Pian Cha≤± 20ns/ days.Suggestion about the distribution method of 1us-1.5us split-second precision reference index:

" sky net " in-flight time Frequency Synchronization net, relies on the Big Dipper or GPS by setting up the split-second precision benchmark of Three-Dimensional Solution algorithm side Bi Dui≤± 300ns after receiving four satellites.The receiver journey of excellent performance, the Big Dipper/GPS all can obtain the superhigh precision time reference with UTC Ke Huo get ≤± 50ns.Unique defect is that security reliability is limited with cost height compared with earth mat.

And the split-second precision frequency device that " earth mat " is supporting body by the optical communication network extended in all direction forms, and " " frequency synchronization section existing clear and definite suggestion in ITU distributes the proposed specifications of the frequency drift value of 18us to earth mat by G811, G813.The overwhelming majority has left terminal and last " several kilometers " communications network clock for, and time synchronized, have two reasons, the overwhelming majority is the time server relying on GPS to be formed, and is kept by " sky net ", is equivalent to the accurate method of synchronization.Once GPS, namely " sky net " breaks down, and the maintenance of time precision is very difficult, in 3G epoch and forthcoming 4G epoch, to the very high 1 ~ 1.5us of the requirement of time precision.The time drift index of this 1 ~ 1.5us refers to air interface stomion.Wireless and wired, or the time interval deviation between wireless and wave point, whenever all necessary≤1 ~ 1.5us.In the Synchronization Network of the novel unified integration of level Four super high precision temporal frequency Synchronization Network composition, the time of equipment and transmission network, its accurate transmission damage was $\&le;\&PlusMinus;\sqrt{1^2+1^2+2^2+5^2+{10}^2+{20}^2+{20}^2}=\&PlusMinus;30.52\mathrm{ns}.$ That is connect at the adjacent base station of two adjacent provinces, cities and autonomous regions.Obviously the maximum that the time interval deviation leaving base station air interface for allows is 960ns ~ 1460ns.Namely relax the time drift tolerance limit amount of last " one kilometer " network, to base station to the flexible tolerant space of all kinds of air interface, thus the reliability of whole temporal frequency Synchronization Network can be ensured.

Claims (8)

1. a method for the asymmetric difference accurate measurement of time delay, is characterized in that:

1) in split-second precision frequency BITS equipment, set up optical communication transmission network network, by optical communication transmission network network passing time reference signal between the synchronizer of MS master-slave station, main website and slave station time synchronized adopt two-way pumping station mode;

2) time interval deviation of following calculated with mathematical model MS master-slave synchronizer is adopted:

In 1. formula, Es represents principal and subordinate's relative time-intervals deviation;

E ₀represent principal and subordinate's initial interval deviation;

represent the remaining time drift error of principal and subordinate's Frequency Synchronization after application frequency and phase discrimination zero passage detection Phase Lock Technique;

Δ T _xyt () represents asymmetric difference, i.e. Δ T _xy(t)=| T _x(t)-T _y(t) |, wherein T _xt () represents the time interval value of signal between optical communication transmission network network to slave station clock synchronization device Received signal strength sent by master clock synchronizer, T _yt () represents the time interval value of signal between optical communication transmission network network to master clock synchronizer Received signal strength that slave station clock synchronization device sends;

represent the randomized jitter noise that optical-fiber network is introduced when passing time reference signal;

1. in formula, first three items is completed by long-distance remote control loose coupling frequency and phase discrimination zero passage detection Phase Lock Technique, and control errors is at ± 5X10 ^-14/ sky;

3) three-dimensional time coordinate is adopted to accurately measure Δ T _xyt (): in main website, measure loopback cycle C value, loopback cycle C value is: C=T _xi(t)+T _yit (), i represents bit quantity, chooses nominal period C according to following different loopback cycle C value _markvalue: when the loopback cycle, C was less than 125us, nominal period C _markchoose 125us; When C was less than 250us and was more than or equal to 125us the loopback cycle, nominal period C _markchoose 250us; When C was less than 1ms and was more than or equal to 250us the loopback cycle, nominal period C _markchoose 1ms; A measured value is less than at loopback cycle C, when a described measured value is less than 10ms and is greater than 1ms, nominal period C _markchoose a described measured value; When C was less than 10ms and was more than or equal to a described measured value loopback cycle, nominal period C _markchoose 10ms; When C was less than 100ms and was more than or equal to 10ms the loopback cycle, nominal period C _markchoose 100ms; Another measured value is less than at loopback cycle C, when another measured value described is greater than 100ms, nominal period C _markchoose another measured value described;

Work as T _xi(t)=T _yi(t), Δ T _xit _yiduring (t) ≈ 0, realize master station and follow station two-way pumping station and transmit equal with the propagation delay time of back;

Work as T _xi(t) > T _yitime (t),

Work as T _xi(t) < T _yitime (t),

Namely

by Δ T _xit _yit () precisely measures, realize MS master-slave relative time synchronous.

2. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: described two-way pumping station mode is two-way time code stream comparison.

3. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: the described synchronous precision of MS master-slave relative time that realizes is≤± 20ns.

4. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: the described synchronous precision of MS master-slave relative time that realizes is≤± 10ns.

5. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: the described synchronous precision of MS master-slave relative time that realizes is≤± 5ns.

6. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: the described synchronous precision of MS master-slave relative time that realizes is≤± 2ns.

7. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: the described synchronous precision of MS master-slave relative time that realizes is≤± 1ns.

8. the method for the asymmetric difference accurate measurement of a kind of time delay according to claim 1, is characterized in that: the low phase noise platform adopting split-second precision frequency BITS equipment, makes to measure precision and improves doubly, wherein N represents the number of times of duplicate measurements in 1 second, the time of τ observation test.