Fiber optic cable monitoring method and apparatus including moisture detection and bending loss detection
First Claim
1. A moisture sensing signal generator comprising:
- an electrically operated code signal generating means for generating a fault signal in response to receipt of electrical energy optical modulator means coupled to the code signal generating means for generating a coded optical signal in response to generation of the fault signal, and electrolytic cell means connected electrically to the code signal generating means, the cell means being inactive when dry and being activated in response to contact with water to generate electrical energy and to supply electrical energy to the code signal generating means.
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Abstract
The invention provides a monitor for monitoring the condition of fibre optic communication cables. The system employs one or more of the optical fibres of a cable to monitor the cable structure for damage or kinks. By using two separate laser sources and simultaneously monitoring the optical losses at two distinct and separate wavelengths, the loss signature of the monitored fibre is determined, analyzed and related to the mechanical condition of the cable structure. To monitor splice points for moisture, a special optical splice sensor unit detects any penetration of water into the splice and transmits a coded alarm signal over the monitored fibre to the optical receiver. Every splice location is assigned a unique sensor code. The optical splice sensor is driven by moisture detection cell, which forms a single cell water activated battery. Water entering the monitored splice closure wets the tape, which activates the cell. The cell generates sufficient voltage and current to power timing, code generation and modulator circuits in the sensor unit for an extended period of time. The activated circuit drives a modulator which modulates the light travelling down the fibre. The modulated light is monitored at the equipment office and the address of the alarming sensor decoded.
19 Citations
31 Claims
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1. A moisture sensing signal generator comprising:
- an electrically operated code signal generating means for generating a fault signal in response to receipt of electrical energy optical modulator means coupled to the code signal generating means for generating a coded optical signal in response to generation of the fault signal, and electrolytic cell means connected electrically to the code signal generating means, the cell means being inactive when dry and being activated in response to contact with water to generate electrical energy and to supply electrical energy to the code signal generating means.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An optical splice sensor unit for signalling moisture penetration of a splice closure enclosing spliced ends of two optical fibre cables, the sensor unit comprising:
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splice means in the splice closure for holding in alignment the ends of optical fibres from the respective cables; displacement means for selectively displacing one of the fibre ends of one cable with respect to the respective fibre end of the other cable; signal generating means coupled to the displacement means for selectively actuating the displacement means; and moisture detector means responsive to the presence of moisture in the enclosure for actuating the signal generator means, the moisture detector means comprising a moisture detection cell means for generating a voltage in response to contact of the cell means with water. - View Dependent Claims (10, 11, 12, 13)
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14. A fibre optic cable monitoring system for monitoring the physical condition of at least one single mode optical fibre having first and second ends, the system comprising:
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light signal generating means for generating first and second monitoring signals of light at different wave lengths, the first signal having a wave length selected to produce a significant attenuation in response to macrobending of a fibre along which the first signal is transmitted, the second signal having a wave length selected to provide substantially less attenuation than that of the first signal in response to macrobending of a fibre along which the first and second signals are transmitted, and the wave lengths of the first and second signals being selected to produce similar amounts of attenuation in response to microbending of a fibre along which the two signals are transmitted; means for simultaneously transmitting the two monitoring signals into the first end of the fibre; optical receiver means optically coupled to the second end of the fibre for simultaneously receiving the two monitoring signals; and signal processing means including means for separating the monitoring signals, and means for measuring the magnitudes of the separated signals. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 27)
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22. A fibre optic cable monitoring system for monitoring the physical condition of a plurality of optical fibres each having first and second ends, the system comprising:
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light signal transmitter means including means for generating two monitoring signals of light at different wave lengths and coupler means for transmitting the monitoring signals equally into the first ends of the fibres; optical receiver means comprising a plurality of optical receivers, each optically coupled to the second end of a respective one of the fibres for receiving the monitoring signals; signal processing means comprising a plurality of processors, each operatively connected to a respective one of the receivers for separating the monitoring signals transmitted by a respective one of the fibres and measuring their magnitudes; and
multiplexer means connected to each of the processors for scanning outputs from the processors; andat least one splice in at least one of said fibres and a respective moisture sensing signal generator associated with each said splice for modulating the monitoring signals in response to the sensing of moisture at the splice. - View Dependent Claims (23, 24, 25, 26)
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28. A method of monitoring a single mode optical fibre having a terminal end and a receiving end comprising:
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transmitting along the fibre from the terminal end a first light signal having a first wave length selected to produce significant attenuation of the signal in response to macrobending or microbending of the fibre; simultaneously transmitting along the fibre from the terminal end a second light signal having a second wave length selected to produce significant attenuation of the signal in response to microbending of the fibre and significantly less attenuation of the second signal than that of the first signal in response to macrobending of the fibre; monitoring the two signals at the receiving end; and determining losses in the two signals. - View Dependent Claims (29, 30, 31)
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Specification