return
Optical
fiber test The Windows-NT-
based UNI-4 test system
can be extended in order to perform test functions of cable bundles that contain optical fibers.
The
optical fiber connections allow communication between different points of the internal system of the vehicle with therefore different fiber sections for each cable.
As
it is impossible to establish beforehand how many of these sections are present in a cable bundle, a modular system easily adaptable
to different requirements has been developed.
The
optical, electrical and mechanicalinterfaces for secure coupling with the
elements under test have been developed
in addition to the actual measurement system.
2.
2.1.
2.1.1
2.1.2
2.2.
2.3.
3.
4.
-
-
-
-
-
-
-
-
Physical interface (Autoblock)
Control unit
Microprocessor module - DSS 002
Calibration mode
Test mode
Opto-electronic conversion unit - SDS 007
Analog/Digital conversion module - DSS 003
Optical fiber test equipment configuration
Option
1.
Physical interface (Autoblock)
The physical interface with the connector
of the cable containing the related fiber termination
is purpose-designed, as in the case of the adapters for the electrical
connections.
The upper part (user side) houses a receptacle in which the connector
under test is inserted.
This connector is held in place by a fastening system. The connector is
released automatically
at the end of the test. However, local manual release is also possible
using a button
on the module. When designing the adapter, particular attention was dedicated
to protect the internal fibers.
The fibers are covered by a special sliding cap to protect them against
dust when the connector under test is not inserted.On the inside, the
module is complete with a standardized attachment
for connection, with the conversion module inside the test bed using a
standard length (2 m)
optical fiber. Mixed modules are available for use with modular connectors
that contain
copper and optical fiber cables.
2.
Control unitUsing a special procedure, the control unit tests the attenuation of each individual
fiber under test and checks for any inversions in the wiring of the fibers.
It consists of a rack equipped with VME standard bus, available in two version
with 5 or 11 slots for insertion of expansion modules.
The unit is equipped with a 230Vac main power supply unit.
In particular, the following modules are available for the specific application:
Microprocessor module - DSS 002This is a standard SIXTAU card designed for use in test systems and equipped with its own microprocessor (80C188XL), control logic and RAM and EPROM program memory.
The module is equipped with a software package able to operate in calibration or test mode.
Calibration modeIn this phase the system is connected to a PC to facilitate calibration.
The connection is made using a specific communication interface.
Two operations are possible in calibration mode:
- calibration of the measurement system according to a sample cable
(for compensation, through self-teaching, of losses inside the system due to the couplings).
- Simply insert a sample cable on the bed and activate a specific cycle
to check the loss of the existing cables.
- As the system is extremely stable, this procedure should be activated only during start-up
of the bed or after maintenance.
- definition of the OK/KO thresholds The data defined as above are saved
in the E2PROM inside the module.
2.1.2
Test modeIn this mode, the unit exchanges data with the UNI-4 test unit on a CAN-Bus.
The test system constantly updates the measurements made and is therefore able
to return the information directly to the cable test program without further connections.
All the data measured are available inside the system.
Measurement is carried out according to the methods defined by IEC 874-1 specifications.
For each measurement channel, and therefore for each fiber to be examined, the system has
a relay with voltage-free change over contact that can be used to output the result of the test
(fiber OK / fiber KO) in the case, for example, in which third party test equipment is used.
Opto-electronic conversion unit - SDS 007The conversion module includes the adjustment and conversion interface of the optical signals into electrical signals and vice versa. It is connected to the physical interface modules by optical fibers.
The module is preset for 5 measurement channels.
In particular, each channel is configured as follows:
- stabilized transmitter (with internal feedback) able to emit a beam of light that is conveyed in the optical fiber under test. The emitter diode operates at a wavelength of 665 ±nm with an emitted power of -15dBm. It is factory set using a sample instrument.
- Light signal receiver (to be connecetd to the connector to the other end of the fiber under test) with signal amplifier for conversion of the light signal into a 0-10Vdc normalized electrical signal.
- Differential amplifier with logarithmic output, compensated according to the signal of the sensor located on the emitter.
- Processor driven relay for fiber OK/KO result output
- Functioning of the measurement channel is shown in the sketch.
Analog/Digital conversion module - DSS 003This module is equipped with a multi-channel 16 bit analog-digital converter with sw adjustment of amplification, gain.
It acquires normalized signals from the interface module and makes these available to the control and processing unit in digital form.
Optical fiber test equipment configurationThe control system is supplied in a minimum configuration
for the testing of 5 fibers.
It can be extended to test up to 15 fibers per system.
Several systems can be used at the same time on the same test bed.
The minimum configuration for testing 5 fibers includes:
· 1 5-slot rack
with power supply unit and VME-Bus
· 1 DSS 002 type microprocessor module
· 1 DSS 003 type A/D converter
· 1 5-channel fiber test module type SDS 007
Using a larger rack (11 slots), extensions
of up to 10 and 15 test channels respectively
are possible inserting additional SDS 007 type modules.
For this standard solution the physical adapters are supplied separately
and equipped with a section of fiber for connection to the opto-electronic
conversion modules.
Quantity and type as requested.
OptionUpon request it is possible to integrate the opto-electronic conversion unit
(ref. par. 2.2) directly in the adapter.
This allows an easier management of the system during construction, modification
and commissioning phases.
