User Manual

Fire Safety and security measures
43
Building Technologies A6V10283843_a_en
Fire Safety & Security Products 05.2010
The OTS controller controls the measuring process and performs calculations,
based on the received signal of the temperature profile along the sensor cable. The
outputs/inputs from the OTS controller provides alarm, fault and reset. These sig-
nals can be connected to a fire detection center. To expand the number of in- or
outputs a FibroSwitch can be connected to the OTS controller. To protect the con-
trollers against harsh environmental conditions which normally exist in tunnels. E.g.
(Metal dust from trains wheels and Acidic air from road traffic) and to enable easy
access for maintenance, the OTS controllers must always be installed in a techni-
cal room or a control center.
In most applications, the OTS controllers communicate with additional network
components such as a control center where the actual situation in the tunnel is visi-
ble in a graphical form (e.g. FibroWeb) or with programmable logic controllers
(PLC) which are used for sophisticated control functions.
4.2.4.2 Measuring principle
The FibroLaser system is based on a laser beam being transmitted through a fiber-
optic cable. The fiber-optic cable reflects a small part of the laser radiation along
the entire length of the cable back to the source. The reflected “backscatter” is
measured by a sensor module within the OTS controller.
The laser radiation emitted is reflected back by the fiber optic cable and measured
in different ways:
– Rayleigh scattering
– Stokes scattering
– Antistokes scattering
The Rayleigh scattering has the same wavelength as the laser beam, whereas the
stokes scattering has a slightly higher and the anti-stokes scattering a slightly lower
wavelength. The two stokes scattering types are also referred to as Raman scatter-
ing. While Stokes scattering is temperature-independent, Antistokes scattering is
affected by the thermal energy of the fiber-optic cable’s local temperature. The in-
tensity increases with the temperature. The temperature of the fiber-optic cable
thus results from the intensity ratio between Stokes and Antistokes scattering.
4.2.4.3 System characteristics
The FibroLaser system measures the maximum and average temperature values
along the sensor cable and activates an alarm in case of a fire.
The main characteristics are:
– Continuous fire detection over the entire length of the cable (monitoring up to a
length of four kilometers per FibroLaser™ OTS controller).
– Detection of convected and radiated heat which guarantees reliable fire detec-
tion at its location, even when there are strong wind speeds of up to 10m/s.
– Alarm actuation based on three different alarm criteria (see alarm).
– 128 free programmable zones which allow area related controls such as activat-
ing of exhausted air flaps (see Zoning).
– High spatial resolution – up to 0.5 m (in tunnels normally 3m are used).
– Information concerning the size and the direction of the spread of fire which of-
fers helpful information for the fire brigades and the emergency services.
– Very high reliability also under harsh conditions (e.g. dampness, corrosion) and
high immunity against electromagnetic interference – which occurs in application
such as in train tunnels or cable trays.