Specifications

Chapter 1. Introduction FOMi-E1/T1 Installation & Operation Manual
1-4 Functional Description
1.3 Functional Description
General
This section describes the functional circuitry of FOMi-E1/T1 and focuses
on the requirements for setting the correct configuration of the modem.
See Figure 1-3 for a block diagram of FOMi-E1/T1 circuitry.
Main Principles of
Operation
FOMi-E1/T1 is a high speed data link between computers, routers or
multiplexers.
FOMi-E1/T1 utilizes a Phase Locked Loop (PLL) circuit to recover
jitter-free data and clock from the optical signal. FOMi-E1/T1 converts
electrical signals from the DTE unit into an optical signal using an infrared
light emitting diode at 850 nm, 1300 nm, or a laser diode at 1300 nm or
1550 nm. At the opposite end of the fiber, the optical signal is converted
back into an electrical signal in compliance with the appropriate interface.
Electrical Interfaces
To recover data and clock from the signal, a Phase Locked Loop (PLL) circuit
is utilized. FOMi-E1/T1 provides internal selection for the following electrical
interfaces: (E1) 75Ω unbalanced and 120Ω balanced; (T1) 100Ω balanced.
When FOMi-E1/T1 detects that the electrical interface levels are below
G.703 electrical levels, or if the Bit Error Rate (BER) on the optical interface
is higher than 1 x 10
-5
, the modem transmits an all "1" signal (AIS) to the
optical interface.
When an all "1" signal (AIS) is detected at the optical or electrical interface,
the modem transparently converts the signal and alerts the user via front
panel LEDs and the supervisory port.
Power Supply
The power supply converts from -48 VDC, +24 VDC, 100 VAC, 115/230
VAC input voltage to ±5V output voltage.
G.703 Interface
The modem has the capability of accepting the following digital interfaces:
G.703-E1 (2048 Kbps), or G.703-T1 (1544 Kbps).
Fiber Optic Interfaces
The modem can accept the following fiber optic interfaces:
•
Infrared LED at 850 nm
•
Infrared LED at 1300 nm
•
Laser diode at 1300 nm
•
Laser diode at 1550 nm in the SC, ST, FC optical connectors.