Reasons for using a fibre-optic remote alarm system for infrastructures NEW! Hazard alarm system (GMA): water, heat and fire Intrusion alarm system (EMA): unauthorised entry

Fibre-optic alarm systems for infrastructures

Fibre-optic alarm systems for infrastructures
For monitoring unauthorised entry, water levels
or heat/fire in cable manholes, distribution cabinets or technical rooms


Cable sealing

Sealing technology
for service entries in buildings and cable ducts in manholes and distribution cabinets


Competition among telecommunications services means that high demands are placed on the quality, reliability and availability of transmission paths. All around the clock fibre-optic lines are used for the transfer of large quantities of data, thus creating the expectation of practically 100% availability, especially where individual optical fibres are rented out to customers.

A study commissioned by Hewlett-Packard and carried out by Techconsult has revealed that critical infrastructures tend to break down about four times a year in medium-sized companies in Germany, leading to a total or partial paralysis of operations [1].

The following list shows the proportion of the causes responsible for network failure [2]

- Cable sheath faults                           28%
- Cable joints                                      31%
- Fibre faults                                       19%
- Terminations                                      5%
- Plug connectors                                  1%
- Others                                               16%


Prevention of network failure by monitoring:

Fibre-optic alarm systems for infrastructures (EMA & GMA)
Network failure may be caused either deliberately through unauthorised entry in telecom infrastructures by vandals, for example, or through heat/fire. Another frequently-occurring cause is water entry in cable manholes affecting both connecting joints and transmission components. Remote monitoring of the network with utilisation of Wolf GmbH fibre-optic alarm systems for infrastructures (EMA & GMA), ensures that most network failure can be prevented.



Features and advantages of the fibre-optic alarm systems for infrastructures:

  • Individual, flexible & user-friendly
  • Modular system: all EMA und GMA can be combined individually!
  • Simultaneous monitoring of up to 8 sensors via a single monitoring fibre.
  • Automatic, pin-point monitoring, offline and current-free, thanks to fibre-optic technology.
    Exact localisation is possible if a dead-zone fibre TO Box is used.
  • Monitoring of 2 to ≥ 12 signal lines
  • For distances up to 80 km
  • Temperature resistance -40°C to +70°C
  • Intrusion alarm systems (EMA- VM):
    - Monitoring of access covers
    - Monitoring of people climbing or reaching inside
  • Hazard alarm systems (GMA- VM):
    - Fill-level indication (of water, for example)
    - Temperatures (heat accumulation /fire)
  • Many of the components are reusable

Example of a working model consisting of:

1.    Cable manhole from Mönninghoff

2.    Sensors from Wolf GmbH

2-1  EMA sensors
       For monitoring manhole access covers

2-2  GMA sensors (with dead-zone TO Box)
       For monitoring water levels

3     Corrugated tubing, slit,
       from Fränkische Industrial Pipes:
       To protect the sensor cable and fix
       it in place in the manhole

31% of all network failure is due to joint faults: The main problem here is water entry and subsequent fibre breakage

Why does water entry occur in connecting joints, in fibre-optic
communication systems that are in conformity with DIN EN 50411-2-3:2012?


Faults that occur during
joint assembly or when
cables are subsequently added

Permanently assigned active sources of heat

  • Inadequate preparation of the cable sheath due to a lack of lubricant containing silicone, cable filling compound or pre-lubricated cable sheath materials
  • The cable sheath has not been treated as prescribed (cleaned, roughened, warmed)
  • Kabelabdichtung bei Doppelbelegung am Kabeleinführstutzen
  • Lack of resistance to inner pressure caused by temperature fluctuation in the range -40 °C to +70 °C

Permanently assigned application of cold

O-rings, washers, shaped rubber inserts

  • Rubber gaskets not fitted closely enough
  • Blind closures not fitted or fitted the wrong way round
  • Seals inadequate or unevenly tightened
  • Rubber sealing rings installed
    incorrectly or at an angle
  • Rubber sealing rings not greased
  • Dirt on rubber sealing rings
  • Pulling tapes jammed


Mastic, tapes, pastes

  • Dirt in the seal
  • Dummy plug missing
  • Seals insufficient or
    unevenly tightened
  • Cable Ø too small
  • Too much/little sealing compound
  • Dirt in the sealing compound

The products them-selves (joint fitting)

Joint design:
unstable construction

  • No long-term dent resistance  (30 days)
  • No long-term resistance to internal overpressure during temperature cycling (20 cycles)

Joint design:
unsuitable construction, e.g.

  • for microduct or microcable applications in accordance with
    DIN IEC 60794-5-10, where cable or duct dimensions are small
  • Absence of double-chamber sealing systems for
    armoured cables or cables with a corrugated steel sheath
  • Insufficient tensile strength or bending
    stability of cables and joint fittings

Joints have not been tested under working conditions or have not been tested at all


The standard DIN EN 50411-2-3:2012 has not
been updated in conformity with current
technology for the new generations of…

DIN IEC 60794-5-10
Version 2008 Part 5-10

IEC 60793-2-50

IEC 60793-2-50
Single mode fibres, categories
B1.1, B1.3, B2, B4, B5 and B6t.

Cable faults

Shrinkage of the cable end


Holes in the cable sheath (double sheath)



Plant roots


Extreme temperature fluctuation



  • Not watertight
  • No sealing on the protective duct
  • Blocked drainage
  • No routine manhole checks

Water entry in connecting joints:

Requirements for protective joint casing

The technical requirements for protective boxes and joint boxes
are ontained in DIN EN 61753-1 and DIN EN 50411-2-3. 2012.


In practice, many installed protective boxes and joint boxes do not fulfil the requirements
of DIN EN 61753-1, which explains why joint faults constitute 31% of all network failure.

According to Table A.12 in the standard – wall connecting-boxes, protective boxes, ODF modules and
joint sleeves - Category C controlled environment, the following compliance tests are applicable for joints:

  • Sinusoidal oscillation
  • Shock
  • Temperature cycling
  • Assembly and disassembly of mechanical optical-
    fibre splices, fibre management systems and joint
  • Tensile strength of fibres/cables
  • Axial pressure
  • Torsion
  • Cable bending
  • Impact (Method B)

IEC 61300-2-1

IEC 61300-2-9

IEC 61300-2-22

IEC 61300-2-33

IEC 61300-2-4

IEC 61300-2-11

IEC 61300-2-5

IEC 61300-2-37

IEC 61300-2-12

Problem of water-mixture penetration in connecting joints

Optical fibres installed in cable manholes or underground are sensitive to immersion in water. Contact with
water affects the fusion splice protection (whether crimp or shrink), causing the metal and plastic matrices to disintegrate.


Alkaline water entry that goes unnoticed for a certain time leads to fibre breakage and network failure. This is due to product-specific properties of, for example, materials used when the glass fibres are cabled (fibre dyes, filling compounds, core materials), or to the cable-processing parameters, or to items such as cleaning and marking agents or fusion splice connectors used in the cable assembly process.


Photo 1: Joint damage, Rheinufer

Depending on the pH value of the water mixture, the onset of fibre breakage - with consequent danger of network failure
- can occur within a year (e.g. at pH2-3, as in brown earth, forest floor or the saline earth associated with roads and motorways).


Photo 2: Lab test: immersion at pH2Photo 2: Lab test: immersion at pH2
Photo 3: Lab test: immersion at pH12

Consequences of fibre breakage:

If fibre breakage occurs, the whole cable must be cut and re-spliced, leading
to temporary power cuts, high repair costs and possibly liability costs.


Avoiding network failure by monitoring:

The operating principle of the fibre-optic remote alarm system (EMA & GMA)

Unauthorised entry, heat/fire or water can be promptly detected with the fibre-optic remote alarm system (EMA & GMA) plus network monitoring.

The detection units in the hazard and intrusion alarms are fibre-optic sensors that operate on the
basis of the bending sensitivity of single mode fibres in accordance with ITU-T G.652.D.

EMA sensors: For monitoring the opening of (manhole) covers, break-in and people climbing or reaching inside:

The respective signal generator is triggered if the access covers are opened, or if people climb or reach inside.

GMA sensors: Hazard detection e.g. fill-level indication, detection of water mixtures, accumu-lation of heat or fire:

Each signal generator is triggered on contact with the medium it is designed to detect.

Information from the activated signal generator is transmitted mechanically to the sensor via the differ-ential-pressure signal transmitter.
The monitoring single-mode optical fibre is bent in a defined way within the sensor itself, thus causing a measurable attenuation change.

The sensors in the fibre-optic remote alarm system

The signal generator (3) is external to the sensor, being located at the place to be monitored (access cover, door etc.). It is connected to the sensor via a
mechanical transmission line (2). In the sensor itself (1), the monitoring single-mode optical fibre in the distribution-module (4) is bent in a defined way



Wolf GmbH

Zazenhäuser Straße 52
D - 70437 Stuttgart

Tel.:  +49 (0)711 87 39 41
Fax.: +49 (0)711 87 12 30

Email: Service(at)