Optical cable real time monitoring system
The present invention relates to a kind of communications optical cable real-time monitoring system, belong to the optical communication technique field.
Lightguide cable link as the optical transmission main body often has cable bad connection, aqueous vapor infiltration optical fibre core, the joint contact is bad and optical cable is dug faults such as disconnected.After lightguide cable link has problem, where just be badly in need of knowing failure cause and circuit breakpoint.Usually fault does not cause the interruption of optical cable transmission signals immediately, but causes cable system slowly to degenerate, but must carry out under very urgent situation again its reparation, and this need can know the type and the place of fault on the one hand as early as possible when maintenance; Preferably can accomplish on the other hand to prevent trouble before it happens, the optical fiber that is slowly degenerating is taked to change or maintenance, to avoid the service of losing and expensive reparation.
At present, existing a collection of optical cable monitoring system is used for carrying out the early prediction and the location of Cable's Fault, as adopt moisture sensing signal generator to detect the moisture immersion that obturator is closed up in butt joint, perhaps use the electro optical measurement device that permanently is loaded on end of cable and come the decay of continuous measurement optical cable chronically, but all be difficult to reach the purpose of real-time monitoring.In addition, first method is owing to only from a sampling by optical fiber, can not reflect the transmission situation of each root optical fiber in the optical cable comprehensively, and second method need be added secondary light source and former transmission equipment is changed, and the fault point that can not inform optical fiber wherein.Patent 93104451 grades belong to the above-mentioned type by retrieval.
The objective of the invention is at the problems referred to above, propose the optical power value of each root optical fiber of monitoring,, reach the purpose that only multifiber is detected in real time with an optical time domain reflectometer (OTDR) according to monitoring result control optical switch.
Technical scheme of the present invention is: this optical cable real time monitoring system mainly comprises the light signal sampling, the luminous power test, analyze, and OTDR detects, it is characterized in that every optical fiber is connected with the input of a wavelength division multiplexer (WDM), the output of each WDM all is connected with the light signal sampler, perhaps every optical fiber is connected with the light signal sampler earlier, the output of light signal sampler is connected with the input of a WDM again, another of light signal sampler exports optical power monitor to, the output of the common individual optical power monitor of N (N is monitored optical fiber radical) is all delivered to a front controller and is compared and calculate, the electric control end that exports optical switch to of front controller, the input of optical switch links to each other with an OTDR, and the output of optical switch links to each other with another input of the WDM that is connected every optical fiber.
Above-mentioned optical cable real time monitoring system is characterized in that the output of front controller can be connected with acoustic-optic alarm with display unit, also can be connected by the industrial computer of serial communication with upper level Surveillance center.
Above-mentioned optical cable real time monitoring system, it is characterized in that OTDR test output can be transferred to by the GP-IB interface carries out data preservation, comparative analysis and control and treatment in the industrial computer.
Above-mentioned optical cable real time monitoring system is characterized in that the light signal sampler generally adopts optical coupler, when the signal packet of transmitting in the optical fiber contains monitor signal, adopts the wavelength division multiplexer that adapts with monitor signal.
Above-mentioned optical cable real time monitoring system, it is characterized in that optical power monitor comprises electro-optical detector, preamplifier, analog to digital converter and microprocessor (CPU), the input of electro-optical detector connects the light signal sampler, export preamplifier to, send analog to digital converter to convert digital signal to through amplifying signal, this signals collecting is delivered to front controller by serial data communication again by CPU.
Above-mentioned optical cable real time monitoring system, it is characterized in that optical power monitor also can include only electro-optical detector and preamplifier, convert input optical signal to analog electrical signal output, optical power monitor output is delivered to shared analog to digital converter through the electrical analogue switch and is linked to each other with front controller.
Above-mentioned optical cable real time monitoring system, it is characterized in that optical coupler to the luminous power of input optical fibre by certain branching ratio 3%: 97%-10%: 90% gives two output, and wherein less luminous power output links to each other with optical power monitor.
Above-mentioned optical cable real time monitoring system is characterized in that WDM belongs to the high-isolation type, and its isolation is more than or equal to 40dB.
Above-mentioned optical cable real time monitoring system is characterized in that the additional insertion loss that optical coupler has is less than or equal to 0.3dB.
Above-mentioned optical power monitor, what it is characterized in that described electro-optical detector is high sensitivity, and its responsiveness is greater than 0.8A/W, and the input impedance of described preamplifier should be more than the 400k Ω, makes the electro-optic detection device can survey the luminous power of minimum reaching-70dBm.
Advantage of the present invention is to adopt optical coupler or wavelength division multiplexer that the light signal that transmits in the optical fiber is told sub-fraction to enter optical power monitor, test its luminous power, reach the purpose of optical power change in each root optical fiber of real-time monitoring, less to the transmission influence of light signal in the optical cable simultaneously.
Advantage of the present invention is only to have used the higher OTDR of a cover price in monitoring system, has just realized that by the switching of controlling optical switch volume is little, cost is low with the purpose of the multi-channel optical fibre in the cover OTDR detection optical cable.When testing, OTDR to stop the light source of former transmission equipment end because of the influence of transmitting optical signal in the optical cable, realize two wavelength optical signals of transmission in the optical fiber by the wavelength division multiplexer (WDM) of high-isolation, promptly the wavelength of optical signal that transmits in the wavelength of optical signal that uses in OTDR test and the optical cable is different, has so also avoided the light signal of OTDR detection usefulness to influence the test of optical power monitor.
The maximum characteristics of the optical cable monitoring system that the present invention proposes provide real-time monitoring and the detection that a kind of new method realizes optical cable.First advantage of this method is to adopt optical passive component to realize above-mentioned functions, and is stable and reliable for performance.Second advantage is to realize real-time with the signal of telecommunication, test speed is fast, if directly use optical switch to come the loop test multifiber, the frequent switch that optical switch does not stop a moment will shorten its working life, and when the more and each survey of light path number is intact when leaving phase buffer, the test interval of each path is just longer, possibly can't in time measure Cable's Fault.The 3rd advantage is that the whole system volume is little, and be easy for installation, needn't draw the alarm signal of transmission equipment, therefore need not change original equipment hardware, also can close according to any multichannel array of customer requirements.
In the accompanying drawing:
Fig. 1 is the system block diagram of first embodiment of the invention;
Fig. 2 is the light path and the circuit connection diagram of arbitrary optical fiber of monitoring among first embodiment;
Fig. 3 is the system block diagram of second embodiment;
Fig. 4 is the light path and the circuit connection diagram of arbitrary optical fiber of monitoring among second embodiment;
Fig. 5 is the schematic diagram of optical power monitor;
Fig. 6 is the schematic diagram that the another kind of embodiment of optical power monitor is connected with front controller;
Fig. 7 is the software logic block diagram of front controller;
Fig. 8 is the electrical schematic diagram of optical power monitor and front controller.
λ 1 represents the wavelength of transmitting optical signal in the optical fiber in the accompanying drawing, the wavelength of optical signal that λ 2 is launched when representing OTDR to detect,
Represent light to connect,
Representative is electrically connected,
Numeral on the line among Fig. 8 is the number of line.Further specify principle of the present invention and embodiment below in conjunction with accompanying drawing, WDM realizes the light signal that transmits in the monitored optical fiber to divide to transmission by the different backs of selecting of wavelength with the light signal that OTDR uses among the figure, and does not disturb mutually; Optical coupler is told the light signal of 3-10% as the monitoring light signal from monitored optical fiber; Optical power monitor is used for every road monitoring light signal is carried out the realtime power test, and converts signal of telecommunication output to; Front controller constantly carries out data acquisition to each optical power monitor circularly, write down every road optical signal power value, carry out analyzing and processing then, the luminous power threshold value that reaches setting is just reported to the police, and the switching of control optical switch, simultaneously, also can carry out data communication with upper level Surveillance center, notify the current optical power value of each root optical fiber at once, or the optical fiber that OTDR is connected to appointment is tested etc. by the requirement of Surveillance center; Optical switch switches to OTDR fault optical fiber or specifies optical fiber to measure; OTDR is used for Transmission Fibers is tested and analyzed; The luminous power display unit shows the current optical power value of each bar optical fiber synchronously; The sound and light alarm parts are finished warning function.
Monitored the N bar optical fiber in the optical cable among Fig. 1 simultaneously, played the center control action by front controller, it is made up of microprocessor (CPU) and auxiliary circuit.After obtaining the optical power value of transmitting optical signal in this optical fiber by test monitoring light signal, deliver to front controller and carry out computing, judge any bar fibre circuit fault is arranged, perhaps degenerate gradually, when testing with OTDR if desired, optical switch is switched to tested optical fiber with OTDR test with light signal, and the light signal of the specific wavelength launched of OTDR is just advanced along the optical fiber of transmitting optical signal in the other direction by WDM like this, and the fault point is surveyed.The index path of concrete every optical fiber is shown in Fig. 2, the direct of travel of transmitting optical signal and test light signal when wherein having marked test, and being connected of monitoring and control circuit.Can find out that therefrom the transmission direction of test light signal is reciprocal, promptly be equivalent to upwards advance that it is up that this working method is called WDM towards transmitting terminal from the receiving terminal of transmitting optical signal.
Second embodiment is with the different of first embodiment among Fig. 1 among Fig. 3, by OTDR test behind the WDM is not optical fiber in the optical cable of monitoring system monitoring at the corresponding levels, but by the downward further used optical cable of transmission signals in this monitoring station, it is descending that this working method is called WDM, its control information comes from next stage supervisory control system test after data communication and the result that obtains, such as a certain optical fiber in the next stage System Reports received signal optical cable fault is arranged, control OTDR switched to this optical fiber after this level system obtained information, down bring in and test from the upper end of transmission, reach the purpose of real-time monitoring equally.The index path of concrete a certain optical fiber can see that the light signal that transmitting optical signal and OTDR use in the optical fiber is launched transmission in the same way from Fig. 4.
Fig. 5 is the theory diagram of optical power monitor.Its first kind of embodiment is converted to analog electrical signal by electro-optical detector with the light signal of importing, after amplifying, the process preamplifier delivers to analog to digital converter, be converted into corresponding digital signal (binary coding), by CPU data gathered again and send it to front controller by serial communication interface.Fig. 6 is another kind of embodiment, optical power monitor only comprises the part in the frame of broken lines among Fig. 5, be that electro-optical detector is converted to the signal of telecommunication with the light signal of importing, amplifying the back through preamplifier directly exports in the mode of analog electrical signal, like this, the connection of optical power monitor and front controller is just with last different, and Fig. 6 is exactly the schematic diagram that corresponding optical power monitor is connected with front controller.In Fig. 6, between optical power monitor and front controller, added a shared analog to digital converter, electrical analogue switch by front controller control is connected above-mentioned every road analog signal with analog to digital converter, front controller obtains corresponding digital signal again from analog to digital converter, sample the optical power value of every road optical fiber equally.
Fig. 7 has provided the workflow diagram of front controller.Front controller constantly carries out data acquisition with each optical power monitor circularly, write down every road optical signal power value, carry out analyzing and processing then, the luminous power threshold value that reaches setting is just reported to the police, and the control optical switch switches to fault optical fiber and measures, and proceeds circulatory monitoring then.Do not comprise the part that upper level Surveillance center and front controller carry out data communication among Fig. 7, the work of this part can be finished with interrupt mode by serial line interface, be that front controller is when carrying out above-mentioned workflow, can respond serial at any time interrupts, carry out data communication with upper level Surveillance center, notify the current optical power value of each root optical fiber at once, or the optical fiber that OTDR is connected to appointment is tested etc. by the requirement of Surveillance center.
The embodiment that Fig. 8 provides is when adopting optical power monitor shown in Figure 5, the electrical schematic diagram of optical power monitor and front controller, wherein PIN is a photo-detector, preamplifier adopts operational amplifier C7650, deliver to analog to digital converter AD0820 through amplified analog signal, 8 bit data that convert to are gathered by single-chip microcomputer 87C51 with parallel ways of connecting, finish the luminous power test process.Front controller among Fig. 8 has also adopted a single-chip microcomputer 87C51, by serial communication interface circulate with each optical power monitor in single-chip microcomputer carry out data communication, note the optical power value of every road optical fiber, and the data communication between the industrial computer of upper level Surveillance center also thus interface finish, the input/output interface of this single-chip microcomputer control alarm lamp and optical switch also output to charactron (LC5011) and its display driver circuit (being made up of MC14495 and 74LS138) simultaneously.
Optical cable real time monitoring system of the present invention also has extensibility, and the figure that tests out such as OTDR also can be transferred in the industrial computer by the GP-IB interface and preserve, comparative analysis and processing.
Can also make some other embodiment within the scope of the invention.For example, the signal packet of transmitting in the monitored optical fiber contains pilot signal and then adopts the wavelength division multiplexer that adapts with pilot signal (as the 1510nm signal is arranged in the SDH system, just can adopt 1550/1510nm WDM) replace the optical coupler among the embodiment, tell this signal and be used for monitoring from transmitting optical signal, the purpose of optical coupler extracts the monitoring light signal exactly from monitored optical fiber herein.Equally, each device in this monitoring system block diagram is finished its relevant every function, and other devices of any same function all can adopt.