Unit installation

Installation and Operation Manual Chapter 1 Introduction
FCD-E1 Overview 1-3
For FCD-E1 versions with sublink, the framing mode and the CRC-4 function can
be separately selected for the main link and sublink; therefore, FCD-E1 can also
serve as a framing converter between the user’s equipment connected to the
sublink and the network. For example, FCD-E1 enables the connection of
equipment that does not support the CRC-4 function to networks which use this
function.
The main link has two line interfaces:
• 120Ω balanced line interface, terminated in an eight-pin RJ-45 (ISO 10173)
connector.
• 75Ω unbalanced interface terminated in two BNC coaxial connectors.
The operating mode of the main link interface, DSU or LTU, is user-selectable. In
the DSU mode, the maximum line attenuation is up to 10 dB; in the LTU mode, the
maximum line attenuation is up to 36 dB, which for typical cables translates to a
range of up to 2 km. This allows FCD-E1 to be placed at a distance of up to 2 km
from the transmission equipment.
Optical Main Link
A wide range of fiber optic interfaces complying with ITU-T Rec. G.921 and G.956
is available for FCD-E1, to optimally meet a wide range of system requirements.
FCD-E1 can be ordered with fiber optic interface with laser transmitter for
operation over 62.5/125 micron multimode fibers (typical attenuation –3.5
dB/km), as well as over low-loss 9/125-micron single-mode fibers (typical
attenuation of 0.4 dB/km at 1310 nm, and 0.25 dB/km at 1550 nm). Each option
can be ordered with ST or FC/PC connectors.
Table 1-1 provides information on the characteristics of the optical subsystem,
including the maximum range over typical fiber optic cable.
Table 1-1. Fiber Optic Interface Characteristics
Wavelength
[nm]
Fiber Type
[µm]
Power
Coupled
into Fiber
[dBm]
Receiver
Sensitivity
[dBm]
Optical
Budget
[dB]
Maximum
Receiver
Input Power
[dBm]
Receiver
Dynamic
Range
[dB]
Typical
Maximum
Range
[km] [mi]
850 62.5/125
multimode
–18 –38 20 –10 28 5 3
1310
9/125
single-mode
–12 –34 22 –12 28 55 34
1550 9/125
single-mode
–12 –34 22 –12 28 88 55
All the fiber optic interface options offer high performance and have a wide
dynamic range, which ensures that the receiver will not saturate even when using
short fiber optic cables. Saturation is caused when the optical power applied to the
receiver exceeds its maximum allowed input power, and results in very high bit
error rates.