Instruction manual
FO SERIAL
Page 6
1.
Introduction
The FO SERIAL is a fibre optic modem with different DTE interface X21/V11, V35, V28.
1.1.
DTE Interface
The FO modem can be equipped with different types of interface:
X21/V11 or V35 interface
: for synchronous data transmission at speed of up to 8192 KBPS. Clock can be configured as internal, external or
slaved. Most interface signals can be forced or activated when the connection is established.
V28 interface
: for synchronous data transmission at speed up to 128000 Bps, for asynchronous data up to 115200 Bps. In synchronous
mode clock can be configured as internal, external, or slaved. Most interface signals can be forced or activated when the connection is
established.
1.2.
Conditioning
The FO Serial modem can meet all integration requirements either as a desktop or rack-mount unit with different power-supply configurations
Internal 24-48 V
DC
converter: the modem includes a 24-48 V
DC
power converter, which can be connected to a 48Vdc supply commonly
available in telecom centers.
Rack-mountable card: the 5 V
DC
required by the modem is supplied by the rack in which the card is inserted. The AMS 4, AMS 8 and AMS
16 chassis can be powered from 110/230 V
AC
or 48 V
DC
depending on the type of power module installed with provision for full redundancy
1.3.
Configuration
The FO Serial modem is configured via the serial control port set for VT100 emulation at 19200 BPS with data format of 8 bits, parity none.
The configuration is menu driven with on line help facilities. Only a few keyboard strokes will be required to set and save the FO parameters.
These menus also initiate analog and digital test loops and display a status report and a bit error rate statistics.
Alternatively the modem can be configured using an AT command set which provides access to all modem parameters.
The FO card can also be configured by the CFIP controller card of the AMS16 chassis though its local VT100 mode or TCP-IP Telnet and SNMP
management protocols
2.
FIBRE OPTIC link
The FO modem supports two different fibre optic type : multi-mode or single mode fibre.
2.1.
Multi-mode Fibre
This is the classic fibre optic cabling, the most commonly installed core is 62.5 micrometers and outer cladding size is 125 micrometers. The
modem’s components are compatible with 62.5 and 50 micrometers core.
In multi-mode fibre, the FO uses two different wavelengths the 820 nanometer and 1300 nanometer. These wavelengths allow distance up to 8
kms between two FO.
In multi-mode fibre at 820 nanometers, the modal dispersion is not negligible, but the limit is greater than the fibre attenuation.
The attenuation of the beam is more important in the 820 nanometer than in the 1300 nanometer.
All the calculation of the budget and fibre distance is described in the next paragraph.
Typically the multi-mode fibre is orange.
2.2.
Single-mode Fibre
Single-mode fibre uses a smaller core diameter of 9 micrometer and the cladding size is also 125 micrometer.
In single-mode fibre the FO supports also two different wavelength component, the first is 1310 nanometer and the second is 1550 nanometer.
The attenuation is close to the theoretical attenuation at 1550 nanometer.
Typically the single-mode fibre is yellow.
2.3.
Calculation of the Budget and Fibre Distance
The FO is defined by the DTE Interface and the Fibre Optic Budget at the different wavelength.
The
Fibre Budget
is the difference between the receiver sensitivity and the transmitter power.
On each wavelength, fibre
attenuation
per kilometre is defined.
Between the two FO there are some
connectors
and
splices
.
The connector attenuation is 1 dB, and splice attenuation is 0.05 dB.
A buffer is added into the calculation ( 2 dB ).
Distance = (Fibre Budget) – (Splice Loss) – (Connector Loss) – Buffer
(Fibre Attenuation)
Example: In multimode fibre at 820 nm the attenuation is 3dBm/km, with two connectors (2 dB) and one splice (0.05 dB), the Fibre Budget of FO
8000-M8 is 15 dB.
Distance = 15 – 0.05 – 2 – 2 = 3.6 km (with margin)
3
Example: In single mode 1310 nm attenuation is 0.3 dBm/km and the FO 8000-SL budget is 23 dB Distance = 14 - 0.05 – 2 – 2 = 33 km
0.3
