General
Consequences of unnoticed water leakage in telecommunication splice closures
Competition amongst telecommunication services brings with it high demands on the quality, reliability and availability of optical fibre transmission paths. These paths are used day and night for transferring big quantities of data, and so practically 100 % availability is expected of them, particularly when fibres are rented out singly to customers.
Fault statistics for structural damage, Fibre Optics CT GmbH
Structural damage to cables in ducts | Reference values | |
2915 cable-km | 1778 cable-km | |
Structural damage |
|
|
incl. cable damage |
|
|
1,338 faults/100 cable-km * year 2003 | 39 faults | --- |
0,445 faults/100 cable-km * year 2003 |
| 8 faults |
Without cable faults |
|
|
0,583 faults/100 cable-km * year 2003 | 17 faults | --- |
No. of telecommunications network | 9 | 5 |
Fault statistics 2010-2012 "Water entry in splice closures":
Inofficially, it is well-known that splice closures are often not watertight. This becomes apparent when a closure is opened up for
retrofitting or relaying cables, or if there is increased attenuation. Unfortunately, official statistics are not currently available.
Constant thermo-active heat sources
- Insufficient bonding with the cable sheath due to lubricants containing silicone, cable filling compounds or cable sheath materials containing lubricants
- Incorrect handling of cable sheath (during cleaning, abrading or warming procedures)
- The space between two-cable configurations in a cable leading-in tube cannot be adequately sealed
- Lack of resistance to inner pressure at temps. of -40 °C up to +70 °C
Constant cold application
O-rings, gaskets, moulded rubber parts
- Rubber gaskets are too far away from the cable
- The blank closure has been left out or put in the wrong way round
- The sealing element is insufficiently or unevenly tightened
- Rubber gaskets are inserted incorrectly or tilted
- Rubber gaskets are not lubricated
- Rubber gaskets are dirty
- Fastening ties have got jammed
Mastic, ties, pastes
- Sealing element is dirty
- The blank closure has been omitted
- The sealing element is insufficiently or unevenly tightened
- Cable Ø is too small
- Too much or too little sealing compound
- Sealing compound is dirty
Consequences of water leaking into splice closures
Contact with water mixtures affects the fusion splice protection
(crimp or shrink-type splice protection), as they cause the metal or plastic to disintegrate.
If alkali or basic water leaking is unnoticed over a longer period it leads to fibre breakage and network failure. This may be because of product-specific properties of the cable parameters, e.g. the materials used for cabling the optical fibres (fibre dyes, filling compounds, core materials), or because of installation factors, e.g. cleaning and marking agents or fusion splice connectors used for cable and splice closure components.
If soil has pH values of 2-3, e.g. brown soil or forest floor, or if the soil is saline (near roads or motorways etc.) then fibre breakage may occur within a year after water entry, unless the fault is dealt with in time.
Average pH values:
Brown soil pH 2.2-4.9 Livestock breeding pH < 4 Moorland pH 3-4
Forest floor pH 2.8 Spreading material (grit) pH < 4
If fibre breakage occurs, the whole cable must be cut out.
How can optical fibre water detectors prevent network failure?
Optical fibre water detectors are used to detect and pinpoint the entry of water or chemical mixtures in closed splice closures or collecting tanks. Monitoring is carried out by means of a selected single mode fibre, which is positioned inside the water detector. Detectors can be retrofitted without any interruption of on-going processes. The functional principle is the bending sensitivity of single mode fibres in acc. with ITU-T G.652 or ITU-T G.657. On contact with the target medium, the water detector causes bending of the monitoring single mode fibre and thus a measurable increase in attenuation.
The route should be checked regularly (at least once a month) by carrying out a measurement for each fibre type, to detect any discrepancies in relation to the reference measurements taken initially at the acceptance of the route. In this way, attenuation increase (e.g. caused by an activated detector) or other incidents can be discovered in good time. If a water detector has been activated, the fault can be corrected and the attenuation increase remedied.
This ensures that network failure can be avoided.
How can water detectors prevent network failure?
Optical fibre water detectors are used to detect and pinpoint the entry of water or chemical mixtures in closed splice closures or collecting tanks. Monitoring is carried out by means of a selected single mode fibre, which is positioned inside the water detector. Detectors can be retrofitted without any interruption of on-going processes. The functional principle is the bending sensitivity of single mode fibres in acc. with ITU-T G.652 or ITU-T G.657. On contact with the target medium, the water detector causes bending of the monitoring single mode fibre and thus a measurable increase in attenuation.
The route should be checked regularly (at least once a month) by carrying out a measurement for each fibre type, to detect any discrepancies in relation to the reference measurements taken initially at the acceptance of the route. In this way, attenuation increase (e.g. caused by an activated detector) or other incidents can be discovered in good time. If a water detector has been activated, the fault can be corrected and the attenuation increase remedied.
This ensures that network failure can be avoided.
Advantages gained by using water detectors
- Reliable detection of leakage
- Economical monitoring
- Simple, quick installation or retrofitting at any time
- Detection of leaks over distances of more than 80 km at short or big leak intervals
- No disturbance of on-going processes: the water detector in operation fulfils the requirements laid down by DIN EN 60793-2-50 and IEC 86A/1343/CD:2010
- No activation at a relative humidity of less than 70 %
- Savings on repair costs caused by fibre breakage
