CN111181631A - Relay submarine optical cable disturbance monitoring system based on time division space division multiplexing - Google Patents
Relay submarine optical cable disturbance monitoring system based on time division space division multiplexing Download PDFInfo
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- CN111181631A CN111181631A CN201911358654.0A CN201911358654A CN111181631A CN 111181631 A CN111181631 A CN 111181631A CN 201911358654 A CN201911358654 A CN 201911358654A CN 111181631 A CN111181631 A CN 111181631A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/077—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using a supervisory or additional signal
- H04B10/0771—Fault location on the transmission path
Abstract
The invention relates to a system for monitoring disturbance of a submarine optical cable with a relay based on time division and space division multiplexing. The detection optical signal generates a backward Rayleigh scattering signal in each section of transmission optical fiber, is coherent with a local optical signal in the optical fiber interferometer to generate a disturbance monitoring signal of the section of submarine optical cable, and enters an uplink optical fiber of the uplink transmission optical fiber through the filter and the optical fiber coupler to be transmitted back to the demodulation equipment. The pulse width of the optical signal is n times of the round-trip delay of each relay section, and the uplink transmission optical fiber comprises at least n uplink optical fibers. The demodulation equipment distinguishes each section of disturbance monitoring signals according to different uplink optical fibers and pulse leading edge time, and analyzes and pre-warns the state of each section of submarine optical cable. The invention directly transmits the disturbance monitoring signal back to the demodulation equipment based on OFDR, time division and space division multiplexing, and realizes the segmented disturbance monitoring and positioning of the submarine optical cable with the length of more than 1000 km.
Description
Technical Field
The invention relates to a distributed optical fiber sensing system, in particular to a time-division space-division multiplexing based trunked submarine optical cable disturbance monitoring system for long-span physical safety monitoring and shore-based detection combining uplink transmission disturbance monitoring signal time division multiplexing and space division multiplexing.
Background
Submarine optical cables are communication transmission cables laid on the seabed and are important components of the internet and other underwater optical networks. However, the submarine optical cable is easily damaged, and the submarine optical cable may be damaged by earthquakes, ship anchors, fishing nets and the like, and even may be damaged artificially. At present, each section of an electrical relay submarine optical cable is connected with a relay amplifier to compensate the transmission loss of an optical signal on the section of optical fiber and amplify the optical signal to the original power level. The submarine Optical cable with the electric relay generally adopts a COTDR (Coherent Detection OTDR, OTDR Optical time domain Reflectometer), so as to realize the health Detection of the Optical fiber link, and has the functions of checking the signal gain of each amplifier on the whole Optical fiber link, whether the Optical cable is broken, positioning a breakpoint and the like.
However, COTDR cannot realize the optical cable disturbance monitoring function similar to phi-OTDR, and thus cannot early warn the destructive behavior in real time, and cannot provide technical support for preventing the destructive behavior.
The optical cable disturbance monitoring technology used on the land currently only supports a monitoring range of about 100km at most, the double-end detection can only reach 200km, the optical cable disturbance monitoring technology cannot cross a relay amplifier of an optical cable at the bottom of the sea, and the requirement of the ultra-long span monitoring range of the optical cable with an electric relay cannot be met.
An Optical Frequency Domain Reflectometer (OFDR) is a high-resolution optical fiber measurement technology developed gradually in the 1990 s, different from a common Optical Time Domain Reflectometer (OTDR), the OTDR carries out optical fiber diagnosis and measurement by emitting a time domain pulse signal, detecting pulse flight time and utilizing the proportional relation between the pulse flight time and a target distance, and the OFDR carries out optical fiber diagnosis and measurement by emitting a continuous frequency modulation laser signal, detecting the beat frequency between target reflected light and local oscillator light and utilizing the proportional relation between the beat frequency and the target distance. The OFDR has higher sensitivity and higher resolution than the OTDR, but the frequency modulation light source of the OFDR has high technical difficulty and high cost, and the phase demodulation difficulty of disturbance signals is high, so that no report for monitoring disturbance of submarine optical cables is found at present.
The currently researched and developed relay submarine optical cable disturbance monitoring system based on underwater sampling adopts an OFDR technology, a detection optical signal emitted by a shore-based light source is transmitted in a downlink manner across relays, submarine optical cable disturbance is detected in a segmented manner, and each segment is respectively transmitted back in a digital sampling manner, so that the disturbance monitoring of a long-span electric relay submarine optical cable with the length of more than 1000km is realized. The underwater sampling and relaying submarine optical cable disturbance monitoring system adopting the frequency modulation continuous wave technology has larger average power than a downlink detection optical signal of an OTDR extension technology, has higher signal-to-noise ratio of optical signal amplification, and is more suitable for long-distance detection of cross-relay. However, using digital sampling backhaul, active modules would have to be added within the subsea repeater amplifier or subsea node, reducing the reliability of the subsea repeater or subsea node.
According to the currently researched and developed submarine optical cable disturbance monitoring system with the relay based on shore-based detection, a multi-wavelength frequency modulation pulse light source is used as a downlink detection optical signal, a disturbance monitoring analog optical signal is directly returned, adjacent sections are subjected to uplink transmission by combining time division multiplexing of the disturbance monitoring signal and a mode of alternately selecting the wavelength of the disturbance monitoring signal, the problems that beat frequency spectrums and optical wavelengths of the disturbance monitoring optical signals of the sections are overlapped and a single fiber cannot be multiplexed are solved, and the submarine cable cross-relay disturbance monitoring in a DWDM mode is realized only by occupying a plurality of optical wavelength channels of a pair of optical fibers. However, since a frequency-modulated pulse light source using multiple wavelengths needs to be configured, there is a problem that the submarine optical cable disturbance monitoring equipment is expensive.
Disclosure of Invention
The invention aims to provide a time division and space division multiplexing-based electric relay submarine optical cable disturbance monitoring system, which is based on an OFDR technology, wherein a detection light source outputs a frequency modulation pulse light signal to be connected into a downlink transmission optical fiber, and the downlink transmission optical fiber of each relay section is connected with an optical fiber interferometer behind a downlink relay amplifier and then is connected to the downlink relay amplifier of the next section through the downlink transmission optical fiber. The detection optical signals generate backward Rayleigh scattering signals in the downlink transmission optical fiber of each relay section, are coherent with the local optical signals of the optical fiber interferometer, generate disturbance monitoring signals of the submarine optical cable of the relay section, are accessed to the filter of the relay section, enter an uplink optical fiber of the uplink transmission optical fiber through the optical fiber coupler of the relay section, enter the uplink relay amplifier of the section connected with the uplink optical fiber, and finally are transmitted back to the demodulation equipment through the uplink optical fiber. The width of the frequency modulation laser pulse is n times of the round-trip delay of the submarine cable relay section, the uplink transmission optical fiber comprises at least n uplink optical fibers, the n uplink optical fibers are subjected to space division multiplexing and return to disturbance monitoring signals of each relay section of the submarine cable, the demodulation equipment distinguishes the disturbance monitoring signals of each section according to different uplink optical fibers and the leading edge time of the pulse, data are analyzed and demodulated, and the safety state of the submarine cable of each relay section is warned. The invention realizes subsection detection of submarine optical cable disturbance, and directly transmits disturbance monitoring optical signals back to shore-based demodulation equipment through time division multiplexing and space division multiplexing, thereby realizing disturbance monitoring and positioning of long-span electrified relay submarine optical cables with the length of more than 1000 km.
The invention designs a system for monitoring disturbance of a submarine optical cable with a relay based on time division space division multiplexing, which comprises a detection light source, a relay amplifier, a downlink transmission optical fiber, an optical fiber interferometer, an uplink transmission optical fiber and demodulation equipment, wherein a detection light signal output by the detection light source is accessed into the downlink transmission optical fiber of the submarine optical cable, each section of the downlink transmission optical fiber is firstly connected with one downlink relay amplifier, and the detection light signal is amplified to the power level transmitted by the detection light source so as to ensure long-distance transmission; the optical fiber interferometer is connected behind the downlink relay amplifier and then connected with the downlink transmission optical fiber of the section; the length of the optical fiber between two adjacent downlink relay amplifiers is less than or equal to 100km, and the optical fiber is called a relay section; each relay section of the system also comprises a filter and an optical fiber coupler, and the transmission wavelength of the filter is consistent with the central wavelength of the detection light source; the detection light source is a single-wavelength frequency modulation pulse light source, the frequency modulation pulse width of a detection light signal is n times of the round-trip delay of one relay section of the submarine optical cable, and n is an integer from 2 to 8; the frequency modulation pulse period is larger than the full-length round-trip delay of the submarine optical cable with the relay to be monitored; the uplink transmission optical fiber of each relay segment comprises at least n uplink optical fibers; the detection light signal sent by the detection light source enters the optical fiber interferometer of a certain relay segment and is divided into two beams, one beam is transmitted downwards along the downlink transmission optical fiber of the segment, and the other beam is used as a local light signal; the backward Rayleigh scattering signal generated by the downlink transmission optical fiber of the relay section is coherent with the local optical signal in the optical fiber interferometer to generate a disturbance monitoring signal of the submarine optical cable of the relay section, the disturbance monitoring signal output by the optical fiber interferometer of the section is accessed into the filter of the relay section, the filter only transmits the disturbance monitoring signal, the output end of the filter is connected with one uplink optical fiber in the uplink transmission optical fiber through the optical fiber coupler of the relay section, and then is accessed into the uplink relay amplifier connected with the uplink optical fiber. The disturbance monitoring signals of n continuous relay sections sequentially select the first uplink optical fiber to the nth uplink optical fiber in the uplink transmission optical fibers for uplink feedback, and the disturbance monitoring signals of the next group of n continuous relay sections sequentially select the first uplink optical fiber to the nth uplink optical fiber in the uplink transmission optical fibers for uplink feedback, so that the adjacent disturbance monitoring signals in the same uplink optical fiber are prevented from being overlapped in a time domain. Disturbance monitoring signals of all relay sections returned by the uplink transmission optical fiber are respectively digitally sampled by n sampling channels of sampling equipment and then transmitted to demodulation equipment, and the sampling equipment comprises a photoelectric conversion module and an analog-to-digital conversion module, wherein the photoelectric conversion module is used for photoelectrically converting optical signals into electric signals and then converting the electric signals into digital signals in an analog-to-digital mode. The demodulation equipment distinguishes the disturbance monitoring signals of each relay section, analyzes and demodulates data, and warns the safety state of the submarine optical cable of each relay section.
Because the coherent heterodyne integration time of the backward Rayleigh scattering signals of each point of the downlink transmission optical fiber of each relay section is in a reverse proportional relation with the length from each optical fiber interferometer, namely the longer the distance is, the shorter the coherent heterodyne integration time is, the unfavorable for the disturbance detection of the optical fiber with the longer distance from the optical fiber interferometer in the relay section is, the scheme of combining time division multiplexing and space division multiplexing is adopted for the invention.
The backward Rayleigh scattering signal generated by the detection optical signal in the downlink transmission optical fiber of a certain relay section is coherent with the local optical signal, the pulse rising edge of the detection optical signal enters the optical fiber interferometer to output the disturbance monitoring optical signal, and when the pulse falling edge of the detection optical signal enters the optical fiber interferometer, the disturbance monitoring signal generated by coherence is a pulse signal with the same pulse width as the detection optical signal of the detection light source, and because the pulse width is larger than the round-trip delay of one relay section of the submarine optical cable, the backward Rayleigh scattering signal at the farthest position of a certain relay section of the submarine optical cable can be coherently received.
The uplink transmission optical fiber at least comprises n uplink optical fibers, the number of the uplink optical fibers participating in uplink transmission of the submarine optical cable disturbance detection signal is n, and n is equal to the multiple of the round-trip delay of the pulse width of the detection light source relative to a relay section of the submarine optical cable. The filter of 1 to n hops transmits each segment of disturbance monitoring signals obtained through filtering, the filter of the segment is connected with a 1 × 2 optical fiber coupler of the segment, the 1 × 2 optical fiber coupler of the Xth hop selects the Yth uplink optical fiber to carry out beam combination, Y is X mod n, namely Y is the remainder obtained by dividing X by n, but Y is not equal to 0, when X is divided by n, Y is n, and Y is 1 to n. Different relay sections of the same uplink optical fiber disturb monitoring signals, and pulse time delay is different due to different positions of the relay sections. The leading edges of the perturbation monitoring signal pulses of adjacent hops differ by one hop round trip delay difference. The invention selects the first to the nth uplink optical fibers of the uplink transmission optical fibers to transmit the disturbance monitoring pulse signals through 1 to n relay sections, avoids the superposition of the disturbance monitoring pulse signals with the same wavelength and the pulse width larger than the pulse delay difference of the adjacent relay sections in the time domain, namely, the disturbance monitoring signals of each relay section are reused for the n uplink optical fibers through space division multiplexing and time division multiplexing. And the demodulation equipment distinguishes the disturbance monitoring signals of different relay sections according to different uplink optical fibers and pulse leading edge time.
The detection light source, the sampling device, the demodulation device, the downlink relay amplifier, the optical fiber interferometer, the filter, the optical fiber coupler and the uplink relay amplifier of the relay section I are shore-based devices at the same end.
In the best scheme, n is 2, the chirp width of the probe optical signal is 2 times of the round-trip delay of one relay section of the submarine optical cable, and the first to nth uplink optical fibers of the uplink transmission optical fiber comprise at least 2 uplink optical fibers. Each filter section is connected with the 1 x 2 optical fiber coupler of the section, and the 1 x 2 optical fiber coupler selects and combines the uplink optical fibers connected with the filters of the section which are separated from the section by one section.
The pulse width of the detection light source is slightly less than n times of the round-trip delay of the relay section, and the difference between the pulse width and the n times of the round-trip delay of the relay section is 20 nanoseconds to 1 microsecond. A certain time gap is reserved between the pulses of the detection optical signals of the adjacent relay sections, pulse overlapping of disturbance monitoring signals of the adjacent relay sections is avoided, and the disturbance monitoring signals of different relay sections can be distinguished conveniently.
The optical fiber interferometer is an MZ optical fiber interferometer (Mach-Zehnder interferometer ) and comprises an optical fiber branching unit, an optical fiber circulator and a 3dB optical fiber coupler, the splitting ratio of the optical fiber branching unit is (5/95) - (50/50), the detection optical signals are divided into 2 paths in the optical fiber branching unit, one path of detection optical signals with large splitting ratio is accessed to a first port of the optical fiber circulator and then is output by a second port of the optical fiber circulator and is accessed to downlink transmission optical fibers for continuous downlink transmission; the detection optical signal with small splitting ratio output by the optical fiber splitter is used as a local optical signal to be accessed into the 3dB optical fiber coupler; backward Rayleigh signals generated on the downlink transmission optical fiber return to the optical fiber circulator from the second port of the optical fiber circulator, the third port of the optical fiber circulator is connected to the 3dB optical fiber coupler to be coherent with local optical signals, and the 3dB optical fiber coupler outputs submarine optical cable disturbance monitoring signals of the downlink transmission optical fiber of the trunk section.
The MZ fiber optic interferometer is respectively connected with a depolarizer on an interference arm of local oscillator light of a 3dB fiber coupler connected with an optical splitter and an interference arm of backward Rayleigh scattering signals of the 3dB fiber coupler connected with an optical circulator before entering the 3dB fiber coupler, so that the influence of polarization modulation is reduced, and the coherence performance is improved.
The system is additionally provided with a disturbance monitoring branch of the branch sea optical cable. A trunk submarine optical cable is connected to a branch submarine optical cable at a certain trunk section, 1 or 2 uplink optical fibers are correspondingly added to the uplink transmission optical fibers for transmitting disturbance monitoring signals of the branch submarine optical cable, a 1 multiplied by 2 optical fiber splitter of a detection optical signal on the downlink transmission optical fibers is divided into 2 paths, and one path is continuously transmitted downwards along the downlink transmission optical fibers and enters an optical fiber interferometer of the trunk section; and the other path of the disturbance monitoring signal enters a branch cable optical fiber interferometer, the detection optical signal passes through the branch cable optical fiber interferometer and then continues to be transmitted downwards along the branch sea optical cable, a backward Rayleigh scattering signal generated on the branch sea optical cable is coherent with a local optical signal thereof on the branch sea optical cable optical fiber interferometer to obtain a disturbance monitoring signal of the branch sea optical cable, the disturbance monitoring signal of the branch sea optical cable is transmitted and filtered by a branch cable filter, then is accessed into an uplink optical fiber for transmitting the disturbance monitoring signal of the branch sea optical cable in an uplink transmission optical fiber through a 1 multiplied by 2 optical fiber coupler of a main sea optical cable, is transmitted upwards to shore-based sampling equipment, and is then connected to demodulation equipment.
When N branch devices are connected in series on the trunk sea optical cable, N is less than the total number of the relay sections of the system; when the length of the branch sea optical cable connected with each branch device is less than or equal to the trunk submarine optical cable trunk length, and the distance between two adjacent branch devices is more than 2 times of the trunk submarine optical cable trunk length, only one uplink optical fiber needs to be added, and the disturbance monitoring signals of each branch sea optical cable are transmitted by adopting a time division multiplexing method; when the length of the branch sea optical cable connecting each branch device is less than or equal to the trunk submarine optical cable trunk length, and the distance between two adjacent branch devices is greater than the trunk submarine optical cable trunk length and less than 2 times of the trunk submarine optical cable trunk length, 2 uplink optical fibers are needed to be added, and the method of combining space division multiplexing and time division multiplexing is adopted to transmit the disturbance monitoring signals of each branch sea optical cable; so as to avoid that the pulses of the disturbance monitoring signals of the branch sea optical cables of two adjacent branch devices do not overlap.
Compared with the prior art, the system for monitoring the disturbance of the submarine optical cable with the relay based on time division and space division multiplexing has the advantages that: 1. the problem that the submarine optical cable disturbance monitoring system cannot penetrate through the repeaters of all sections of the submarine optical cable is solved, the detection distance of the submarine optical cable disturbance monitoring system is increased from within 100km to thousands of kilometers, and the requirement of physical safety real-time monitoring of the long-span submarine optical cable is met; 2. the monitoring system does not need a digital sampling module, and does not need to increase active equipment on the seabed, and the monitoring system adopts underwater whole-course optical signal transmission; 3. the detection light source only uses one wavelength, so that the equipment cost is reduced; 4. the downlink frequency modulation pulse signal only occupies 1 channel of one downlink optical fiber and can be in wavelength division multiplexing with other digital communication service signals; the upstream submarine cable monitoring signals only occupy 1 channel of each of the n upstream optical fibers, and can also be subjected to wavelength division multiplexing with other digital communication service signals; 5. supporting disturbance monitoring of a branch sea optical cable of the submarine optical cable; disturbance monitoring of the branch sea optical cable is realized while disturbance monitoring of the main cable is completed; 6. the scheme of the invention based on OFDR technology can not only completely replace COTDR equipment, but also complete real-time disturbance monitoring and positioning and submarine cable fault point positioning, the coherent integration time of the equipment in unit time is more than 1000 times of the coherent integration time of the COTDR, the sampling and signal processing of coherent signals can be completed in second-level time, and the equipment greatly improves the response speed and response sensitivity of the equipment relative to the response speed of ten-minute-level of the COTDR.
Drawings
FIG. 1 is a schematic structural diagram of a disturbance monitoring system 1 of a relayed submarine optical cable based on time division and space division multiplexing;
FIG. 2 is a schematic diagram of a single-wavelength disturbance monitoring pulse time domain structure of a disturbance monitoring system of a trunked submarine optical cable based on time division and space division multiplexing in embodiment 1;
FIG. 3 is a schematic structural diagram of an MZ fiber optic interferometer of embodiment 1 of a disturbance monitoring system for a submarine optical cable with a relay based on time division and space division multiplexing;
fig. 4 is a schematic structural diagram of a disturbance monitoring system embodiment 2 of a relayed submarine optical cable based on time-space division multiplexing.
Detailed Description
Embodiment 1 of a system for monitoring disturbance of submarine optical cables with relays based on time division and space division multiplexing
The structure schematic diagram of embodiment 1 of the system for monitoring the disturbance of the submarine optical cable with the relay based on time division and space division multiplexing is shown in fig. 1, wherein a detection light signal output by a detection light source is accessed into a downlink transmission optical fiber of the submarine optical cable, each section of the downlink transmission optical fiber is connected with a downlink relay amplifier, an optical fiber interferometer is connected behind the downlink relay amplifier, and then the section of the downlink transmission optical fiber is connected; the length of the downlink transmission fiber between two adjacent downlink relay amplifiers in this example is 100km, which is called a trunk. The detection light source is a single-wavelength narrow-linewidth frequency modulation pulse light source, the frequency modulation pulse width of a detection light signal is 2 times of the round-trip delay of one relay section of the submarine optical cable, and the frequency modulation pulse period is larger than the round-trip delay of the whole length of the submarine optical cable with the relay to be monitored.
The uplink transmission optical fiber of each relay segment in this example comprises 2 uplink optical fibers participating in transmission of the disturbance monitoring signal of each relay segment.
Fig. 1 is a schematic structural diagram of an i-th relay segment and an ii-th relay segment in this embodiment, a detection light signal output by a detection light source is accessed into an i-th downlink relay amplifier, i.e., a downlink EDFA i, of the i-th relay segment, and then accessed into an optical fiber interferometer i, and then connected with an i-th downlink transmission optical fiber, a backward rayleigh scattering signal generated by the detection light signal in the i-th downlink transmission optical fiber is coherent with a local optical signal of the optical fiber interferometer i, and a disturbance monitoring signal of the submarine cable of the relay segment is generated, the disturbance monitoring signal output by the optical fiber interferometer i is accessed into a filter i of the i-th relay segment, and the disturbance monitoring signal transmitted by the filter i through the i-th sea cable enters an uplink EDFA of an uplink optical fiber a in the uplink transmission optical fiber i through an optical fiber coupler i of the i-th relay segment, and is finally returned to a sampling channel of a sampling device through the uplink optical. The structure of an optical fiber interferometer II of the second relay section is the same as that of the optical fiber interferometer I of the first relay section, disturbance monitoring signals output by the optical fiber interferometer II are accessed to a filter II of the second relay section, the disturbance monitoring signals transmitted by the filter II enter an uplink EDFA IIb of an uplink optical fiber IIb through an optical fiber coupler II of the second relay section, and finally the disturbance monitoring signals are transmitted back to a b sampling channel of sampling equipment through the uplink optical fiber b and are output to demodulation equipment through digital sampling. One uplink optical fiber a in the uplink transmission optical fibers transmits disturbance monitoring signals of the relay sections I, III, V, VII and the like, and the other uplink optical fiber b transmits disturbance monitoring signals of the relay sections II, IV, VI, VIII and the like. And the demodulation equipment distinguishes the disturbance monitoring signals of different relay sections according to different uplink optical fibers and signal pulse leading edge time. Fig. 2 shows a schematic diagram of a pulse time domain structure of a disturbance monitoring signal transmitted by 2 uplink optical fibers in this example.
In this example, the disturbance monitoring signals of the relay sections I, III, V, VII and the like are combined and bundled on the uplink optical fiber a, and the disturbance monitoring signals of the relay sections II, IV, VI, VIII and the like are combined and bundled on the uplink optical fiber b.
The pulse width of the detection light source is slightly less than 2 times of the round-trip delay of the relay section of the submarine optical cable, namely 2ms-0.5 mus.
the fiber optic interferometer ③ of this embodiment is an MZ interferometer, as shown in FIG. 3, comprising a fiber optic splitter, a fiber optic circulator and a 3dB fiber coupler, wherein the splitting ratio ③ of the splitter is 90:10, a detection light signal is divided into 2 paths in the fiber optic splitter, wherein one path ③ of the detection light signal with a large splitting ratio is accessed to a first port ③ of the fiber optic circulator and then is output by a second port ③ of the fiber optic circulator and is accessed to a downlink transmission fiber for continuous downlink transmission, the detection light signal with a small splitting ratio output by the splitter is accessed to the 3dB fiber optic coupler as a local light signal, a backward Rayleigh signal generated on the downlink transmission fiber is returned to the fiber optic circulator by the second port ③ of the fiber optic circulator and is accessed to the 3dB fiber optic coupler by a third port ③ of the fiber optic circulator to be coherent with the local light signal, and the 3dB fiber optic coupler outputs a submarine optical cable disturbance monitoring signal ③ of the downlink transmission fiber ③ of the trunk section.
In the MZ fiber optic interferometer of the embodiment, a depolarizer is respectively connected to an interference arm of local oscillator light of a 3dB fiber coupler connected to a fiber splitter and an interference arm of backward Rayleigh scattering signals of the 3dB fiber coupler connected to a fiber circulator before entering the 3dB fiber coupler, and the embodiment adopts a Lyot depolarizer.
The basic structure of the system is similar to that of example 1, but a disturbance monitoring branch of a branch sea cable connected to the branch equipment is added. Fig. 3 is a schematic structural diagram of a trunk section of a trunk submarine optical cable to which a branch device is connected, in this example, 5 branch devices are connected in series on the trunk submarine optical cable, and when the length of the branch submarine optical cable connected to each branch device is less than or equal to the trunk submarine optical cable trunk section length and the distance between two adjacent branch devices is greater than 2 times of the trunk submarine optical cable trunk section length, only one uplink optical fiber c needs to be added to transmit disturbance monitoring signals of 5 branch submarine optical cables by a time division multiplexing method. In fig. 3 the trunk is connected to 1 branch sea cable via 1 branch device. The detection optical signal is divided into 2 paths in a 1 x 2 optical fiber splitter, one path is continuously transmitted downwards along the downlink transmission optical fiber of the main submarine optical cable, the other path is connected to a branch cable optical fiber interferometer, the detection optical signal passes through the branch cable optical fiber interferometer and then is continuously transmitted downwards along the branch submarine optical cable, a backward Rayleigh scattering signal generated on the branch submarine optical cable is coherent with a local optical signal thereof in the branch cable optical fiber interferometer to obtain a disturbance monitoring signal of the branch submarine optical cable on the relay section, the disturbance monitoring signal of the branch submarine optical cable is sent to a branch cable optical fiber coupler through a branch cable filter, and is combined with a signal of an uplink optical fiber c transmitting the disturbance monitoring signal of the branch submarine optical cable in an uplink transmission optical fiber, the uplink signal is transmitted to a sampling channel c of a branch submarine optical cable sampling device, and the sampled signal is sent to a demodulation device.
If 5 branch devices are connected in series on the trunk submarine optical cable, the length of the branch submarine optical cable connected with each branch device is less than or equal to the trunk submarine optical cable relay section length, and the distance between two adjacent branch devices is greater than the trunk submarine optical cable relay section length and less than 2 times of the trunk submarine optical cable relay section length, 2 uplink optical fibers are needed to be added, namely the uplink optical fiber c and the uplink optical fiber d are added, and the method of combining space division multiplexing and time division multiplexing is adopted to transmit disturbance monitoring signals of 5 branch submarine optical cables; to ensure that the pulses of disturbance monitoring signals of two adjacent branch devices do not overlap.
The above-described embodiments are only specific examples for further explaining the object, technical solution and advantageous effects of the present invention in detail, and the present invention is not limited thereto. Any modification, equivalent replacement, improvement and the like made within the scope of the disclosure of the present invention are included in the protection scope of the present invention.
Claims (8)
1. A system for monitoring disturbance of a submarine optical cable with a relay based on time division and space division multiplexing comprises a detection light source, a relay amplifier, a downlink transmission optical fiber, an optical fiber interferometer, an uplink transmission optical fiber and demodulation equipment, wherein a detection light signal output by the detection light source is accessed into the downlink transmission optical fiber of the submarine optical cable, and each section of the downlink transmission optical fiber is connected with one downlink relay amplifier; the optical fiber interferometer is connected behind the downlink relay amplifier and then connected with the downlink transmission optical fiber of the section; the length of the optical fiber between two adjacent downlink relay amplifiers is less than or equal to 100km, and the optical fiber is called a relay section; the method is characterized in that:
each relay section also comprises a filter and an optical fiber coupler, and the transmission wavelength of the filter is consistent with the central wavelength of the detection light source;
the detection light source is a single-wavelength frequency modulation pulse light source, the frequency modulation pulse width of a detection light signal is n times of the round-trip delay of one relay section of the submarine optical cable, and n is an integer from 2 to 8; the frequency modulation pulse period is larger than the full-length round-trip delay of the submarine optical cable with the relay to be monitored;
the uplink transmission optical fiber of each relay segment comprises at least n uplink optical fibers; the detection light signal sent by the detection light source enters the optical fiber interferometer of a certain relay segment and is divided into two beams, one beam is transmitted downwards along the downlink transmission optical fiber of the segment, and the other beam is used as a local light signal; the backward Rayleigh scattering signal generated by the downlink transmission optical fiber of the relay section is coherent with the local optical signal in the optical fiber interferometer to generate a disturbance monitoring signal of the submarine optical cable of the relay section, the disturbance monitoring signal output by the optical fiber interferometer of the section is accessed into the filter of the relay section, the filter only transmits the disturbance monitoring signal, the output end of the filter is connected with one uplink optical fiber in the uplink transmission optical fiber through the optical fiber coupler of the relay section, and then is accessed into the uplink relay amplifier connected with the uplink optical fiber. Disturbance monitoring signals of n continuous relay sections sequentially select a first uplink optical fiber to an nth uplink optical fiber in the uplink transmission optical fibers for uplink feedback, disturbance monitoring signals of a next group of n continuous relay sections sequentially select disturbance monitoring signals of each relay section returned by the first uplink optical fiber in the uplink transmission optical fibers, the disturbance monitoring signals of each relay section are respectively digitally sampled by n sampling channels of sampling equipment of each uplink optical fiber and then transmitted to demodulation equipment, and each sampling equipment comprises a photoelectric conversion module and an analog-to-digital conversion module, wherein the photoelectric conversion module is used for photoelectrically converting optical signals into electric signals and then performing analog-to-digital conversion on the electric signals into digital signals; the demodulation equipment distinguishes the disturbance monitoring signals of each relay section, analyzes and demodulates data, and warns the safety state of the submarine optical cable of each relay section;
and each section of disturbance monitoring signals obtained by the transmission of the filters of 1 to n relay sections is connected with the 1 × 2 optical fiber coupler of the section, the 1 × 2 optical fiber coupler of the Xth relay section selects the Y-th uplink optical fiber for beam combination, Y is X mod n, namely Y is the remainder obtained by dividing X by n, Y is not equal to 0, and when X is divided by n, Y is n.
2. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to claim 1, wherein:
the n is 2, the frequency modulation pulse width of the detection optical signal is 2 times of the round-trip delay of one relay section of the submarine optical cable, and the uplink transmission optical fiber comprises at least 2 uplink optical fibers; each filter section is connected with the 1 x 2 optical fiber coupler of the section, and the 1 x 2 optical fiber coupler selects and combines the uplink optical fibers connected with the filters of the section which are separated from the section by one section.
3. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to claim 1, wherein:
the pulse width of the detection light source is slightly smaller than n times of the round-trip delay of the relay section, and the difference between the pulse width and the n times of the round-trip delay of the relay section is 20 nanoseconds to 1 microsecond.
4. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to any one of claims 1 to 3, wherein:
the detection light source, the sampling device, the demodulation device, the downlink relay amplifier, the optical fiber interferometer, the filter, the optical fiber coupler and the uplink relay amplifier of the relay section I are shore-based devices at the same end.
5. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to any one of claims 1 to 3, wherein:
the optical fiber interferometer is an MZ optical fiber interferometer and comprises a splitter, an optical fiber circulator and a 3dB optical fiber coupler, the splitting ratio of the optical fiber splitter is (5/95) - (50/50), a detection optical signal is divided into 2 paths in the optical fiber splitter, wherein one path of detection optical signal with a large splitting ratio is accessed to a first port of the optical fiber circulator and then is output by a second port of the optical fiber circulator and is accessed to a downlink transmission optical fiber for continuous downlink transmission; the detection optical signal with small splitting ratio output by the optical fiber splitter is used as a local optical signal to be accessed into the 3dB optical fiber coupler; backward Rayleigh signals generated on the downlink transmission optical fiber return to the optical fiber circulator from the second port of the optical fiber circulator, the third port of the optical fiber circulator is connected to the 3dB optical fiber coupler to be coherent with local optical signals, and the 3dB optical fiber coupler outputs submarine optical cable disturbance monitoring signals of the downlink transmission optical fiber of the trunk section.
6. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to claim 5, wherein:
the MZ fiber optic interferometer is respectively connected with a depolarizer on an interference arm of local oscillator light of a 3dB fiber coupler connected with an optical splitter and an interference arm of backward Rayleigh scattering signals of the 3dB fiber coupler connected with an optical circulator before entering the 3dB fiber coupler.
7. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to any one of claims 1 to 3, wherein:
adding a disturbance monitoring branch of a branch sea optical cable; a trunk submarine optical cable is connected to a branch submarine optical cable at a certain trunk section, 1 or 2 uplink optical fibers are correspondingly added to the uplink transmission optical fibers for transmitting disturbance monitoring signals of the branch submarine optical cable, a 1 multiplied by 2 optical fiber splitter of a detection optical signal on the downlink transmission optical fibers is divided into 2 paths, and one path is continuously transmitted downwards along the downlink transmission optical fibers and enters an optical fiber interferometer of the trunk section; and the other path enters a branch sea optical cable optical fiber interferometer, the detection optical signal passes through the branch sea optical cable optical fiber interferometer and then continues to be transmitted downwards along the branch sea optical cable, backward Rayleigh scattering signals generated on the branch sea optical cable are coherent with local optical signals thereof on the branch sea optical cable optical fiber interferometer to obtain disturbance monitoring signals of the branch sea optical cable, the disturbance monitoring signals of the branch sea optical cable are transmitted and filtered by a branch cable filter, then are accessed into an uplink optical fiber for transmitting the disturbance monitoring signals of the branch sea optical cable in an uplink transmission optical fiber through a 1 x 2 optical fiber coupler of the main sea optical cable, are transmitted upwards to shore-based sampling equipment and then are connected to demodulation equipment.
8. The time-space division multiplexing based trunked undersea optical cable disturbance monitoring system according to claim 7, wherein:
when N branch devices are connected in series on the trunk sea optical cable, N is less than the total number of the relay sections of the system; when the length of the branch sea optical cable connected with each branch device is less than or equal to the trunk submarine optical cable trunk length, and the distance between two adjacent branch devices is more than 2 times of the trunk submarine optical cable trunk length, only one uplink optical fiber is added, and the disturbance monitoring signals of each branch sea optical cable are transmitted by adopting a time division multiplexing method; when the length of the branch sea optical cable connecting each branch device is less than or equal to the trunk submarine optical cable trunk section length, and the distance between two adjacent branch devices is greater than the trunk submarine optical cable trunk section length and less than 2 times of the trunk submarine optical cable trunk section length, 2 uplink optical fibers are added, and the method of combining space division multiplexing and time division multiplexing is adopted to transmit the disturbance monitoring signals of each branch sea optical cable.
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| CN116707583B (en) * | 2023-07-31 | 2023-10-13 | 国家海洋技术中心 | Deep sea coupling relay transmission system applied to underwater platform |
| CN117392796B (en) * | 2023-12-11 | 2024-03-22 | 云南保利天同水下装备科技有限公司 | Partition detection method, partition detection system and defense detection assembly thereof |
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