Purely transparent transmission method of time start moment in optical wavelength division multiplexing transmission system

Abstract

The present invention discloses a method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system, which transmits the time start moment of a time base and provides multiple high-quality, long-distance optical transmission channels at the same time. The method for pure transparent transmission of the time start moment uses n wavelength channels among the many wavelengths of wavelength division multiplexing to achieve pure transparent transmission of the time start moment, and implements dispersion compensation based on the relative dispersion deviation value and relative dispersion slope difference value obtained by "same-length comparison and dynamic dispersion precision monitoring" and "same-length comparison and relative dynamic dispersion precision monitoring" in the system, so that the number of available wavelength channels is greater than that of the usual available wavelength channels. The present invention synchronizes the constant nominal delay of each relay segment, which is independent of the actual distance of optical fiber transmission; and can filter out multiple random change noises generated during optical fiber transmission to make the optical wave transmission dispersion adaptively matched and smoothly balanced.

Description

Technical Field

[0001] The invention belongs to the field of precision measurement and transmission technology, and relates to an optical wavelength division multiplexing transmission system of time synchronization technology, in particular to a method for pure transparent transmission of the time start moment of the optical wavelength division multiplexing transmission system. Background Art

[0002] The timing accuracy of the land-based timing system is closely related to the stability and accuracy of the time synchronization network and frequency synchronization network of the optical network. Whether the excellent, extremely stable and extremely accurate time and frequency reference number of the high-time clock source group (eHPRTC / HPRTC) in Beijing, my country is transmitted transparently to locations more than 5000km away without damage, non-degradation, safe and reliable, high availability and high credibility, according to the current Beidou timing accuracy level (<10ns), when my country's Beidou satellite navigation timing system is destroyed and unavailable, my country's land-based timing system can continue to provide military and civilian users with "non-degradation, safe and reliable and highly available "transparent" transmission of high-precision time and frequency reference timing information" by relying on the optical network, so as to achieve the purpose of integrated PNT between the sky and the earth. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] A method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system transmits the time start moment of a time base and provides multiple high-quality, long-distance optical transmission channels at the same time. The method for pure transparent transmission of the time start moment uses n wavelength channels among the many wavelengths of wavelength division multiplexing to achieve pure transparent transmission of the time start moment, and dispersion compensation based on relative dispersion deviation values ​​and relative dispersion slope difference values ​​obtained by "same-length comparison and dynamic dispersion precision monitoring" and "same-length comparison and relative dynamic dispersion precision monitoring" is implemented in the system, so that the number of available wavelength channels is greater than the usual number of available wavelength channels.

[0006] Furthermore, each wavelength channel in the same wavelength division multiplexing system obtains the synchronous clock and time origin from the transmission channel at the start time, thereby optimizing the transmission quality of the channel and achieving transmission quality indicators consistent with the existing transmission system while increasing the transmission distance relative to the existing system.

[0007] Furthermore, the relative frequency drift and relative phase drift must be eliminated at the start time.

[0008] Furthermore, the three wavelength channels that realize pure and transparent transmission at the time start moment implement the multi-wave common viewing method to make the starting moment pure and the "zero-crossing alternating" downlink transmission reach the An node.

[0009] Furthermore, the above three waves or seven waves are selected in an orderly manner to avoid the accumulation of phase drift.

[0010] Furthermore, the above method uses the same length comparison to implement compensation for different dispersion slope drift accumulations and different transmission delays caused by different wavelengths.

[0011] Furthermore, the services of the synchronization clock and time start moment of the above transmission channels are that each node in the system uses the time start moment and synchronization clock obtained by the time wavelength channel as a companion clock to provide timing for other wavelength channels.

[0012] Furthermore, the pure transparent transmission method at the time start moment described above is a "three-wave co-viewing" downward transmission in the same direction.

[0013] Furthermore, the rising edge instantaneous jitter is sent at the above starting moment for orderly selection, and a new type of frequency and phase discrimination is adopted.

[0014] The present invention has the following beneficial effects:

[0015] 1) The present invention synchronizes the delay of each relay segment to a constant nominal value, which is independent of the actual distance of the optical fiber transmission;

[0016] 2) Filter out multiple random noises generated during the optical fiber transmission process to achieve adaptive matching, smooth equalization and compensation of light wave transmission dispersion;

[0017] 3) The accumulated delay drift introduced by ultra-long distance nonlinear asymmetry, mismatch, etc. is firmly controlled within the range of 1 / 2a0, that is, MTIE and TDEV are intelligently controlled to be constants within a certain observation and measurement time, that is, they do not change with time, and the "steady random process" remote control phase locking is realized step by step.

[0018] 4) A precise transmission method without loss of time (moment) and without degradation.

[0019] 5) Make the time frequency completely unified and highly consistent hierarchical cloud synchronization.

[0020] 6) The noise level of each node depends only on the background noise of the clock.

[0021] 7) The accuracy of monitoring time depends only on the measurement scale of the time interval.

[0022] 8) The application of time interval pilot is the infrastructure construction of network synchronization.

[0023] 9) There is no difficulty in keeping time in all-optical network synchronization, that is, the "timekeeping" technical indicator is no longer considered.

[0024] 10) Each optical fiber can be set with several frame synchronization time interval pilot transmissions, which always ensures the transparent, accurate, stable, safe, reliable and robust transmission of the physical quantity "time" to any place in the world.

[0025] 11) Optical network synchronization provides the possibility of improving the synchronization accuracy of 5G network wireless synchronization.

[0026] 12) The present invention is an important means to improve the time synchronization accuracy of Beidou and satellite communications to a high degree of consistency. DETAILED DESCRIPTION

[0027] The present invention is described in further detail below:

[0028] The time start moment pure transparent transmission method of the optical wavelength division multiplexing transmission system of the present invention transmits the time start moment of the time base and provides multiple high-quality, long-distance optical transmission channels at the same time. The time start moment pure transparent transmission method uses n wavelength channels among the many wavelengths of wavelength division multiplexing to achieve pure transparent transmission of the time start moment, and implements dispersion compensation based on the relative dispersion deviation value and relative dispersion slope difference value obtained by "same length comparison and dynamic dispersion precision monitoring" and "same length comparison and relative dynamic dispersion precision monitoring" in the system, so that the number of available wavelength channels is larger than that of the usual available wavelength channels. The rising edge instantaneous jitter is sent at the start moment for orderly selection, and a new type of frequency discrimination and phase discrimination is adopted.

[0029] The present invention obtains the synchronous clock and time origin of the transmission channel at the time start moment for each wavelength channel in the same wavelength division multiplexing system, thereby optimizing the transmission quality of the channel and achieving the transmission quality index consistent with the existing transmission system while increasing the transmission distance relative to the existing system. And the relative frequency drift and relative phase drift must be eliminated at the start moment. The service of the synchronous clock and time start moment of the transmission channel is that each node in the system uses the time start moment and the synchronous clock obtained by the time wavelength channel as the accompanying clock for the timing supply level of other wavelength channels. The pure transparent transmission method of the time start moment is the "three-wave co-viewing" downlink co-directional transmission.

[0030] Among them: 3 wavelength channels are used to achieve pure and transparent transmission at the time start. These 3 channels implement the multi-wave common view method to make the start time pure and the "zero-crossing alternating" downlink transmission reach the An node. Three or seven waves are selected in an orderly manner to avoid phase drift accumulation. The same length comparison is used to implement compensation for different dispersion slope drift accumulation and different transmission delays caused by different wavelengths.

[0031] In order to facilitate understanding of the solution of the present invention, the present invention is further described in detail below:

[0032] The pure transparent transmission of the time start moment mentioned in the present invention is to transmit the signal representing the time start moment in the transmission network to any node of the network and the equipment of the user who needs to use the timing service, and ensure that the time when the signal arrives is the same as the time when the start signal is generated. Such a characteristic of the transmission system is called pure transparent transmission of the time start moment. Pure transparent transmission can achieve the pure transparent transmission of the time start moment to the place where the timing user needs to use it.

[0033] The present invention first gives the concept of pure transparent transmission of optical fiber, which requires the definition of "optical routing" to be clarified first: the transmission delay of a single optical wave frequency λa from the optical fiber of A→B or B→A is the delay value from the start time of Tx electrical pulse to the end time of Rx recovery electrical pulse, which is defined as the "optical routing" of the optical wave frequency λa. It includes the sum of the delays including the delay of optical wave frequency from Tx electrical interface EO transformation processing delay and Rx recovery OE transformation processing delay, which is called "optical routing". Multiple random changes in the transmission process of optical wave λa are also included. Therefore, according to the basic requirement of the physical quantity "time": time must be a continuous and uninterrupted transmission. Then the transparent transmission of the untimed time pilot λt is that the transmission route of λt in the DWDM wavelength division in the "optical routing" of A→B must be direct. It is not allowed to transform into other λi. If λt is still λt after optical crossover, it is transparent transmission. SDH transmission has "pointer adjustment". If the optical crossover optical wave frequencies randomly alternate with each other, random changes of "phase step" will occur.

[0034] The current communication technology is developing towards high-speed, large-capacity, and long-distance data. When working at 40Gbps and higher-speed WDM optical transmission systems, especially long-distance WDM systems, for example, for 40Gbps non-return-to-zero (NRZ) pulse optical transmission, tunability greater than 200ps / nm, peak-to-peak GVD non-uniformity (GVD-group velocity dispersion) less than 10ps, and PMD less than 1ps within a wavelength of 0.5nm are required. As a result, the threshold of dispersion drift accumulation will become the main factor limiting the development of optical fiber communication towards high speed, large capacity, and long distance. For example, in a 40Gbps system, the dispersion drift needs to be accurately controlled within less than 50ps / nm. When the bit rate is increased to 160Gbps, only 5.0ps / nm is required. What are the requirements for 200G / 400G / 800G? Of course, it is smaller. That is to say: the accuracy of all-optical network synchronization for future big data, high-speed, large-capacity, and long-distance optical communication networks must reach ps level end-to-end, for example, their multi-point MAC control OLT ONU requires "precision time tag synchronization" and "precision synchronization timing" accuracy (strictly speaking, it should be called frame header ordered timing synchronization matching transmission technology) must reach ps level. It requires all-optical network digitization and synchronization to achieve. Otherwise, it is difficult to achieve high-speed, large-capacity optical communication data transmission over a distance of more than 5000km.

[0035] In addition, when the optical relay distance is less than 20km (please note: the transmission delay of light waves in optical fibers varies in the range of 4.89550ns / km to 4.89761ns / km to 4.89899ns / km. Therefore, different optical frequencies produce different delay changes, and the fiber length varies with temperature, that is, the fiber length changes with time), when the frame period is selected (for example, 8000PPS phase comparison phase detection) 125μs, consider that the delay value (about 25μs) must be reserved for EO / OE processing for optical routing. Optical Transport Network OTN (please note: the name OTN is defined according to the functions and main features of the network. It does not limit the transparency of the network. The ultimate goal is to achieve fully transparent all-optical network synchronous transmission. In other words: the transparent transmission of the optical wavelength of the optical transmission unit in the DWDM system with an optical fiber length of ≤20km can be achieved by 8000 frames per second. If there are 96 DWDM optical frequencies in use according to the C band), then select CWDM and DWDM in the O, S, and L bands for transmission and complete it with DFB lasers, which will become a good way to expand optical fiber resources. This is an innovative "new DWDM" wavelength division transmission mode. The network architecture of the new NSOTN all-optical network synchronous transmission in the "fully transparent mode" can be completed. (Please note: 125μs is only a frame structure and there are 250μs / 500μs... and other frame periods available). If the O, S, and L bands of a single optical fiber can all achieve DWDM wavelength division transmission, its transmission capacity will increase by more than 3 times? If O, S, and L waves are fully utilized, it will have great practical significance. Therefore, the three optical wave frequencies λ+iλtλ-i are selected in each optical cable to "disassemble" from the traditional DWDM system to establish a relatively independent synchronous support network, which is the supporting infrastructure of the basic technology to ensure the normal operation and maintenance of the optical transmission network. The full utilization of the O, S, and L bands of optical fiber resources is one of the independent innovation technologies in the all-optical network. It is a technology that does not compete with traditional optical transmission communication services for the "golden band". It is one of the major technical measures to ensure network security. Therefore, the development of O, S, and L band optical wave transmission is a good way to make full use of optical fiber strategic resources.

[0036] The common view transmission technology originated from long-distance satellite communication. The present invention innovatively applies the principle of "common view" to the optical fiber transmission network. The "three-wave common view" technology solves the effective suppression, compression and filtering of the drift accumulation of extremely slow parasitic noise in the optical fiber transmission process at the start of time synchronization. Since optical fiber transmission is not affected by adverse factors such as atmospheric electromagnetic wave interference, it is believed that transparent transmission of optical fiber transmission is one of the core transmission technologies that can currently achieve ns transmission> 5000km time synchronization. When Mastr is eHPRTC with a stability and accuracy of 1E-16, how to "transparently, without damage, without degradation, safe and reliable and highly reliable" transmit this extremely accurate time frequency reference signal to a place more than 5000km away is a technical problem that we must solve? The "multi-wave common view" transmission phase comparison principle can improve the synchronization effect by more than 10 times. In addition, the design of multi-path high-precision multi-function comparison and phase comparator based on FPGA is completed, and then the effect of this principle is verified and practiced through experiments, and it is certified as pure transparent transmission. It is one of the key core technologies at the start of long-distance transmission. They are all based on the premise that the starting moment of the physical quantity "time" of the time-frequency reference signal must be transmitted continuously, purely and transparently.

[0037] The secondary slope of optical transmission in the CWDM / DWDM transmission process of optical fiber transmission optical communication network, such as the secondary slope of dispersion coefficient, is the main factor causing nonlinear asymmetry and mismatch of optical fiber "information" transmission, and is one of the main reasons for drift accumulation at the start time. Therefore, the dispersion slope difference must be 100% compensated, and this must be done in DWDM and wavelength division multiplexing frequency to ensure that the dispersion difference between high frequency and low frequency is basically filtered out. Only in this way can large-capacity, high-speed, and ultra-long-distance data transmission be achieved.

[0038] The allocation method is set according to the 10ns time synchronization technical requirements of the land-based timing system:

[0039] 5000km = 100 × 50km, a total of 101 transmission devices, allocated to the end-to-end indicators:

[0040] For example, A→←B 5000km=100×50km (or 50×100km, 200×25km, etc.)

[0041] When the land-based timing system indicator is 10ns, the MTIE of the A→B system is ≤±7.05ns. The end-to-end indicator allocated to a relay segment is:

[0042] 100km:

[0043] 50km:

[0044] 25km:

[0045] This shows that in the design of the long-distance time and frequency benchmark for the OTN all-optical network, it is very important to measure and evaluate the end-to-end indicators with "ps" level time synchronization accuracy as the basis for the design and measurement indicators.

[0046] Assuming the master station is the HPRTC (1E-15 / day) clock source group, the HPRTC zero-distance loosely coupled extremely low phase noise purified eDCXO type "transparent clock" is the zero-distance slave of the eHPRTC and is transparently transmitted to the Master station clock group in the war zone (using the most precise time interval instrument with 15-bit measurement accuracy to measure) to achieve:

[0047] Relative frequency error compared with the master station HPRTC: ≤±5.0E-16 / day / or 7 days / or 15 days

[0048] Relative phase deviation compared with the master station HPRTC: ≤±62.5ps / day / or 7 days / or 15 days

[0049] Compare the time interval error TID with the master station HPRTC: Ymax-Ymin≤50ps / or 25ps

[0050] (Note: TID—Time Inteival Deviation)

[0051] High-precision digital oscilloscope measurements:

[0052] Multi-channel common view measurement technology can achieve (internal 200GHz time interval measurement scale): 5psXX chip instantaneous jitter ≤ 20ps / 45ps

[0053] Compare the relative phase mean with HPRTC:

[0054] Relative maximum positive deviation value (max) compared with HPRTC: + deviation ≤ ± 1 / 2

[0055] Minimum negative deviation value (min) compared with HPRTC: - Deviation ≤ ±1 / 2

[0056] Compare relative TDEV or SDEV (sdEV) with HPRTC

[0057] The MTIE index of the 5000km land-based timing system can be calculated from the two measurements:

[0058] MTIE≤±705ps (not mean square value but peak-to-peak value of the measurement time interval of 1 day)

[0059] The present invention is a new type of NSOTN network synchronization all-optical network in "full transparent mode", and its optical fiber synchronization support network architecture includes:

[0060] Each all-fiber optical cable can use the three waves of wavelength division multiplexing of one fiber to build a network synchronization support network system architecture for seamless downlink synchronization and pure transparent transmission of the pilot signal before the dedicated time interval, and use the three waves of another fiber to build seamless uplink synchronization. Backhaul is a mode in the "full transparent mode" (dual-fiber bidirectional): as long as they do not interfere with other wavelength division multiplexing and do not affect each other, the important role of the FPGA-based PBSO (Phase-Build-Sync-Out) platform function and performance in pure transparent transmission is realized:

[0061] The innovation of PBSO is to make full use of the stability of the transparent clocks of Master and Slave to transmit purely and transparently, and the synchronization effect of the virtuous cycle of performance and relative frequency synchronization is gradually improved, that is, the Slave "transparent clock" is also the accuracy and stability of the Master main clock. When the synchronization effect is better, there is a high degree of stability and accuracy. The "precise", "accurate" and "fast" separation of three waves, precise phase comparison, phase measurement, and double phase discrimination form a virtuous cycle synchronization. The steady-state step-by-step tracking synchronization accuracy is more than 10 times higher than the current traditional synchronization technology. PBSO and multi-wave common view jointly and innovatively separate the accumulated deviation and precise relative slope difference of the temperature change of optical fiber and the dispersion drift during optical fiber transmission, which can make the three waves of O, S, C and L bands of optical frequency and optical routing compensated by electrical dispersion (PBSO phase matching smooth equalization synchronization alignment compensation, both of which can filter out 100% of the random noise in the optical fiber transmission process. PBSO is combined with optical fiber length bundling to select the appropriate whole frame period to construct a whole frame phase-locked synchronous transmission network network to innovatively realize phase matching smooth equalization compensation alignment, so that the change of the actual length delay of the optical fiber in the optical relay section of optical fiber transmission can also complete the phase smooth equalization digital compensation alignment.

Claims

1. A method for pure and transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system, which transmits the time start moment of a time base and provides multiple high-quality, long-distance optical transmission channels, characterized in that: The method for pure transparent transmission of the time start moment is to use n wavelength channels among the many wavelengths of wavelength division multiplexing to realize pure transparent transmission of the time start moment, and implement dispersion compensation based on the relative dispersion deviation value and the relative dispersion slope difference value obtained by "same-length comparison and dynamic dispersion precision monitoring" and "same-length comparison and relative dynamic dispersion precision monitoring" in the system, so that the number of available wavelength channels is greater than that of the usual available wavelength channels; Each wavelength channel in the same wavelength division multiplexing system obtains the synchronous clock and time origin from the transmission channel at the time start moment, thereby optimizing the transmission quality of the channel and achieving the transmission quality index consistent with the existing transmission system while increasing the transmission distance relative to the existing system; the service of the synchronous clock and time start moment of the transmission channel is that each node in the system uses the time start moment and the synchronous clock obtained by the time wavelength channel as the accompanying clock for timing supply of other wavelength channels; the network architecture of the pure transparent transmission method is the NSOTN network architecture of the full transparent mode, and in the pure transparent transmission process, the PBSO platform based on FPGA separates three waves, accurately compares phases, measures phases, and double phase discriminations, and PBSO and multi-wave common viewing jointly and innovatively separate the accumulated deviation and accurate relative slope difference value of the optical fiber changing with temperature and the dispersion drift during the optical fiber transmission process, so that the optical wave frequency optical routing can compensate the three waves of the O, S, C, and L bands by electrical dispersion.

2. The method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system according to claim 1, characterized in that: The relative frequency drift and relative phase drift must be eliminated at the start time.

3. The method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system according to claim 2, characterized in that: Three wavelength channels are used to realize pure and transparent transmission at the start time. These three channels implement the multi-wave common viewing method to ensure that the start time is pure and the "zero-crossing alternating" downlink transmission reaches the An node.

4. The method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system according to claim 3, characterized in that: Three or seven waves are selected in order to avoid phase drift accumulation.

5. The method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system according to claim 4, characterized in that: The same length comparison is used to compensate for the different dispersion slope drift accumulation and different transmission delays caused by different wavelengths.

6. The method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system according to claim 5, characterized in that: The pure transparent transmission method at the time start moment is to transmit in the same direction with "three waves co-viewing" downward.

7. The method for pure transparent transmission of the time start moment of an optical wavelength division multiplexing transmission system according to claim 1, characterized in that: At the starting moment, the rising edge instantaneous jitter is sent for orderly selection, and a new type of frequency and phase detection is adopted.