Specifications

Chapter 1 Introduction Installation and Operation Manual
1-4 Functional Description FOM-E1/T1 Ver. 2.0
1.3 Functional Description
This section describes the functional circuitry of the FOM-E1/T1 fiber optic
modem. FOM-E1/T1 is used for transmission of E1 (2.048 Mbps) and T1
(1.544 Mbps) over multimode or single-mode fiber optic media. The unit is
transparent to framing and can transmit data using any framing pattern with
HDB3 or B8ZS coded signals.
Figure 1-3 illustrates the FOM-E1/T1 block diagram.
E1/T1 Line
Interface
Transmit Clock
Receive Clock
Receive Data
Transmit Data
CDP
Encoder/
Decoder
RTIP
RRIN
TTIP
TRING
Clock
Recovery
(PLL)
CDP to F/O
Figure 1-3 FOM-E1/T1 Block Diagram
FOM-E1/T1 comprises the following signal processing stages:
• Signal conversion
• Data/clock recovery
• Data transfer.
Signal Conversion
Electrical signals are converted into an optical signal using an infrared light-
emitting diode or laser transmitter. At the opposite end of the fiber, the optical
signal is converted back into an electrical signal and amplified to the required
level.
Data/Clock Recovery
A Phase Locked Loop (PLL) circuit recovers data and clocking from the signal.
FOM-E1/T1 provides internal selection for the E1/T1 electrical interfaces.
Data Transfer
The optical signal is linked to the fiber-optic media and transmitted over the
optical link to the remote unit. The remote unit receives the optical signal into a
high sensitivity pre-amplifier and an AGC (Automatic Gain Control) circuit. The
output of the receiver is applied to the clock recovery circuit and the data
regeneration circuit, which in turn apply it to the electrical interface driving
circuit.