CN100358274C - Synchronized network timing signal transmitting method based on wave division multicomplexing - Google Patents

Abstract

The present invention discloses a synchronized network timing signal transmitting method based on wave division multicomplexing, which at least comprises the steps: A, optical timing channel (OTC) modules take synchronous timing signals and a path of monitoring overhead signals into a path of plesiochronous digital hierarchy (PDH) high order group signals in a multiplexing method at the sending side; B, the plesiochronous digital hierarchy (PDH) high order group signals obtained from the step A are modulated to optical monitoring wavelength of a wave partial system and transmitted by a wave division multicomplexing system; C, the optical timing channel (OTC) modules separate synchronous timing signals and a path of the monitoring overhead signals from received plesiochronous digital hierarchy (PDH) high order group signals by multicomplexing at the receiving side. Compared with the prior timing link technology, the synchronous timing transmission of a dense wave division multicomplexing device of the present invention farthest inherits the technical advantages of the PDH. The present invention avoids the inherent defects of the SDH technology, and simultaneously can use a large number of newly made WDM devices in the existing transmission network to reduce the network building cost.

Description

Synchronization Network timing signal transfer approach based on wavelength division multiplexing

Technical field

The present invention relates to the wavelength division multiplexed optical network technology, specifically describe, relate to a kind of Synchronization Network timing signal transfer approach based on wavelength division multiplexing.

Background technology

Along with the develop rapidly of digital exchange system and SDH (Synchronous Digital Hierarchy) equipment such as (Synchronous Digital Hierachy are called for short SDH), the importance at telecommunications network obviously increases synchronously.Because these equipment all need clock to come for it provides operating frequency, the quality of clock performance will directly influence equipment performance, and the performance during clock work is mainly by the quality decision of self performance and external synchronization signal.The quality of external synchronization signal is guaranteed by Synchronization Network.Synchronization Network is made up of nodal clock equipment and time link.Few through number of nodes, relay system is minimum, and quality is good, the high time link of reliability with fine assurance the whole network synchronously.

The Synchronization Network time link mainly contains two kinds at present, and one is PDH (Pseudo-synchronous Digital Hierarchy) (PlesiochronoousDigital Hierarchy is called for short PDH) time link; Another is the SDH time link.The former mainly adopts the 2Mbit/s passage of PDH to transmit the Synchronization Network timing signal, comprise 2Mbit/s special line and 2Mbit/s service line, its operation principle is that transmission system is carried out positive justification to the 2Mbit/s signal, hands on by the PDH line system, and transmission equipment is not subjected to this 2Mbit/s clock synchronization, therefore, the shake that transmission system is introduced is less with the drift damage, and the PDH transmission network is simple in structure, is convenient to the time link planning and designing, fault location is convenient to regularly recover rapidly.The latter mainly adopts the transmission of STM-N signal regularly, its operation principle is the timing of SDH network element clock run-down lines clock signal, and for the clock signal that sends provides regularly, the Synchronization Network timing signal is carried on the STM-N signal like this, and hands on by the SDH system.SDH network element clock will seal in the time link like this, and SDH network element clock just becomes the nodal clock of Synchronization Network like this, need bring in the management maintenance scope of Synchronization Network.Secondly, on the SDH time link, not only comprise the transmission of timing signal, also comprise the transmission of Synchronization Status Message (SSM).As shown in Figure 1.

The preferred PDH link of present stage time link does not adopt the PDH/SDH compounded link in principle, and when adopting the SDH link, the SDH network element that is connected in series on the reference timing signal transmission link should lack (seeing the ITU-T suggestion for details G.813) as much as possible.

Though the PDH time link has above-mentioned advantage, along with transmission network is developed to SDH by PDH comprehensively, the PDH transmission system certainly will will withdraw from the whole network.

Though the SDH transmission system has become the main body of transmission network, exist some intrinsic shortcomings:

(1) generation of senior clock of rudimentary clock synchronization or timing loop

(2) limited transmission distance (link is introduced reasons such as drift is difficult to filter)

(3) the SDH complicated network structure, protection make the planning of time link become complicated, the fault location difficulty flexibly.

Summary of the invention

At the deficiency in the background technology, the object of the present invention is to provide a kind of Synchronization Network timing signal transfer approach based on wavelength division multiplexing.

The present invention comprises the steps: at least

A, at transmitter side, light timing channel (OTC) module with synchronous timing signal and one the tunnel monitoring overhead signal be multiplexed into one tunnel PDH (Pseudo-synchronous Digital Hierarchy) (PDH) high order block signal;

B, the high order block signal that steps A is obtained are modulated on the light supervisory wavelength of wavelength-division system, and transmit by wavelength-division multiplex system;

C, at receiver side, light timing channel (OTC) module goes out synchronous timing signal and one tunnel monitoring overhead signal by demultiplexing with PDH (Pseudo-synchronous Digital Hierarchy) (PDH) the high order block Signal Separation that receives.

According to technique scheme:

Steps A is meant that the monitoring overhead signal with the synchronous timing signal of three road 2M and one road 2M is multiplexed into 8M PDH (Pseudo-synchronous Digital Hierarchy) (PDH) high order block signal;

Step C is meant the monitoring overhead signal that goes out synchronous timing signal and one road 2M of three road 2M from 8M PDH (Pseudo-synchronous Digital Hierarchy) (PDH) high order block Signal Separation.

Described PDH (Pseudo-synchronous Digital Hierarchy) (PDH) high order block signal is PDH (Pseudo-synchronous Digital Hierarchy) (PDH) quadratic gropup signal at a high speed.

Light timing channel (OTC) module adopts the clock cross unit that synchronous timing signal is dispatched.

Multiplex protocol adopts G.742 standard.

Dispatching method to synchronous timing signal is:

The synchronous timing signal of the outside being imported in first initial station is crossed to Multiplexing Unit, so that the clock that inserts can transmit by WDM;

The synchronous timing signal intersection of demultiplexing unit being recovered in the point of destination outputs to external clock interface output unit, uses so that the clock of WDM transmission can be distributed to other clockwork of Synchronization Network;

The synchronous timing signal that demultiplexing unit is recovered at relay station intersects and outputs to Multiplexing Unit, so as WDM can with the clock that will transmit in wavelength-division system one by one website transmit downwards, up to the point of destination.

The present invention compares with existing time link technology, dense wave division multipurpose (Wavelength DivisionMultiplexed, being called for short WDM) device synchronization regularly transmits because of adopting the PDH multiplex technique to realize that the monitoring expense of synchronous timing signal and wave-division device transmits jointly, do not increasing under the new transmission channel situation of wave-division device, can realize the synchronous timing signal transmission, and on performance, at utmost inherited the advantage of PDH technology, avoided the inherent shortcoming of SDH technology, can utilize simultaneously a large amount of newly-built WDM equipment in the existing transmission network, reduce network construction cost.

Description of drawings

Fig. 1 is the Synchronization Network time link;

Fig. 2 is the position of light timing channel module in wdm system;

Fig. 3 is a light timing channel inside modules structural representation;

Fig. 4 is the synchronous timing signal flow chart of light timing channel inside modules.

Embodiment

Consult shown in Figure 2ly, light timing channel (Optical Timing Channel, the be called for short OTC) basic function of module in system is with Synchronization Network timing signal and the multiplexing and demultiplexing of wdm system service signal.At transmitter side, after synchronous timing signal inserted WDM equipment, the OTC module was multiplexed to the high order block signal with itself and other wavelength-division service signal bit, hands on by wavelength-division multiplex system; At receiver side, the OTC module is given the downstream node clockwork after synchronous timing signal is isolated.

Implementation method of the present invention is: the frame structure of the monitoring overhead signal of WDM is the E1 frame, and synchronous timing signal also is the E1 frame, so just can utilize the high order block signal of the Digital Multiple Connection Technique of PDH agreement with pilot signal and the synthetic high speed of synchronizing signal, be modulated on the supervisory wavelength then and transmit, because the multiplex mode of PDH is the asynchronous multiplexing mode, the low speed signal that respectively is re-used in the frame structure of high speed signal keeps the characteristic of oneself, so can utilize demultiplexing monitoring of separation signal and synchronous timing signal easily from PDH high order block signal at receiving terminal, so both finish the transmission of the monitoring expense of original wave-division device, also finished the transmission of synchronous timing signal simultaneously.

Comprise three parts with reference to 3, one typical OTC modular design of figure: the external clock interface, high speed signal is multiplexing and the professional intersection of clock.Describe specific implementation method of the present invention in detail below in conjunction with this module:

The external clock interface:

This part is mainly finished the synchronous timing signal (as the synchronous timing signal of synchronous nodal clock equipment such as BITS) that will transmit and inserts and output, requirement according to present Synchronization Network, each external clock interface of OTC is all supported 2048kbit/s and two kinds of interface modes of 2048kHz, the physical interface pattern can be by software arrangements, its physical/electrical characteristic conforms ITU-T suggestion regulation requirement G.703.Wherein 2048kbit/s adopts the E1 frame structure, satisfies the ITU-TG.704 suggestion, supports Synchronization Status Message (Synchronization StatusMessage, be called for short SSM) function, the OTC module is left intact to SSM information, is transparent transmission, and reports webmaster; 2MHz does not support the SSM function.The synchronous timing signal that is inserted by the external clock interface is input to the professional cross unit of clock.

High speed signal is multiplexing:

What OTC module high speed signal adopted is the PDH multiplex mode, consider that can not influence original WDM monitors the transmission (receiving sensitivity is very high) of expense and the transmission needs of actual synchronization timing signal, the present invention adopts second-order multiplex, and promptly three road synchronous timing signals (3*2M) are monitored the quadratic gropup signal that expense (2M) is multiplexed into one road 8M with one the tunnel.Detailed process is:

Three road synchronous timing signals by the output of synchronised clock route cross matrix, it is the signal 10,11 and 12 among Fig. 4, become one tunnel at a high speed 8448kbit/s quadratic gropup signal with the monitoring overhead signal (being similarly 2048kbit/s, the E1 frame structure) of wavelength-division multiplex system by the second-order multiplex module.Multiplex protocol adopts ITU-T to advise G.742 standard, utilizes the positive justification technology, and the bit that is used in the fixed position in the frame structure of high speed signal is filled in indication and shown whether the bit of filling in has data-signal;

Then the 8448kbit/s quadratic gropup signal of above-mentioned high speed is modulated on the light supervisory wavelength of wavelength-division multiplex system and is sent to the downstream website by wavelength-division multiplex system;

Receiver side at the downstream website, it is (opposite with multiplex process with one tunnel wavelength-division monitoring overhead signal to utilize PDH quadratic gropup demultiplexing technology to isolate three road synchronous timing signals, fill in that the content that shows the position is removed or reservation bit is filled in the content of position according to bit), three road synchronous timing signals are the signal 4,5 and 6 among Fig. 4, wherein the synchronous timing signal of Hui Fuing sends synchronised clock route cross matrix to, carries out service dispatching.

Clock is professional to intersect:

For making things convenient for the transmission of synchronous timing signal business, management and maintenance, the OTC module provides a small-sized space division cross matrix unit (the intersection particle is 2M) to realize the service dispatching to synchronous timing signal, can (be the signal 1 among Fig. 4 with the synchronous timing signal of external clock interface input by software arrangements, 2 and 3) and the synchronous timing signal that recovers of line side (be the signal 4 among Fig. 4,5 and 6) intersect arbitrarily that to output to the line side (be the signal 10 among Fig. 4,11 and 12) any one tunnel in clock output interface and the external clock output interface (is the signal 7 among Fig. 4,8 and 9).Detailed process:

The synchronous timing signal of the outside being imported in first initial station is crossed to Multiplexing Unit, so that the clock that inserts can transmit by WDM;

The synchronous timing signal intersection of demultiplexing unit being recovered in the point of destination outputs to external clock interface output unit, uses so that the clock of WDM transmission can be distributed to other clockworks of Synchronization Network;

The synchronous timing signal that demultiplexing unit is recovered at relay station intersects and outputs to Multiplexing Unit, so as WDM can with the clock that will transmit in wavelength-division system one by one website transmit downwards, up to the point of destination.

Adopt the present invention, the dense wave division multipurpose device synchronization is regularly transmitted at utmost to inherit the advantage of PDH technology, avoids the inherent shortcoming of SDH technology, can utilize a large amount of newly-built WDM equipment in the existing transmission network simultaneously, reduces network construction cost.

Claims (6)

1, a kind of Synchronization Network timing signal transfer approach based on wavelength division multiplexing is characterized in that comprising the steps: at least

A, at transmitter side, light timing channel module with synchronous timing signal and one the tunnel monitoring overhead signal be multiplexed into one tunnel PDH (Pseudo-synchronous Digital Hierarchy) high order block signal;

B, the high order block signal that steps A is obtained are modulated on the light supervisory wavelength of wavelength-division system, and transmit by wavelength-division multiplex system;

C, at receiver side, light timing channel module goes out synchronous timing signal and one tunnel monitoring overhead signal by demultiplexing with the PDH (Pseudo-synchronous Digital Hierarchy) high order block Signal Separation that receives.

2, the method for claim 1 is characterized in that:

Steps A is meant that the monitoring overhead signal with the synchronous timing signal of three road 2M and one road 2M is multiplexed into 8M PDH (Pseudo-synchronous Digital Hierarchy) high order block signal;

Step C is meant the monitoring overhead signal that goes out synchronous timing signal and one road 2M of three road 2M from 8M PDH (Pseudo-synchronous Digital Hierarchy) high order block Signal Separation.

3, method as claimed in claim 1 or 2 is characterized in that: described PDH (Pseudo-synchronous Digital Hierarchy) high order block signal is PDH (Pseudo-synchronous Digital Hierarchy) quadratic gropup signal at a high speed.

4, the method for claim 1 is characterized in that: light timing channel module adopts the clock cross unit that synchronous timing signal is dispatched.

5, as claim 1,2 or 4 described methods, it is characterized in that: multiplex protocol adopts G.742 standard.

6, method as claimed in claim 4 is characterized in that the dispatching method of synchronous timing signal being:

The synchronous timing signal of the outside being imported in first initial station is crossed to Multiplexing Unit, so that the clock that inserts can transmit by WDM;

The synchronous timing signal intersection of demultiplexing unit being recovered in the point of destination outputs to external clock interface output unit, uses so that the clock of WDM transmission can be distributed to other clockwork of Synchronization Network;

The synchronous timing signal that demultiplexing unit is recovered at relay station intersects and outputs to Multiplexing Unit, so as WDM can with the clock that will transmit in wavelength-division system one by one website transmit downwards, up to the point of destination.

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