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CHAPTER 2: Introduction
2.3 Functional Description
Figure 2-3. T3 Fiber Optic Line Driver block diagram.
The T3 Fiber Optic Line Driver has the following signal-processing modules:
• Signal conversion (see Section 2.3.1)
• Data/clock recovery (see Section 2.3.2)
• Data transfer (see Section 2.3.3)
2.3.1 S
IGNAL
C
ONVERSION
Conversion of the electrical NRZ (non-return to zero) signal into an optical CDP
signal is performed by an infrared light-emitting diode. At the opposite end of the
fiber, the optical signal is converted back into an electrical signal and amplified to
the required level.
2.3.2 D
ATA
/C
LOCK
R
ECOVERY
To recover data and clock from the signal, a Phase Locked Loop (PLL) circuit is
used. The line driver provides internal selection for the T3, 75
Ω
balanced, B3ZS
line coding electrical interface.
2.3.3 D
ATA
T
RANSFER
The optical signal is linked to the fiberoptic media and transmitted via the optical
link to the remote unit. A high-sensitivity pre-amplifier and an AGC (Automatic
Gain Control) circuit enable the remote unit to receive the optical signal. The
output of the receiver is applied to the clock recovery circuit and data regeneration
circuit, which in turn applies it to the electrical interface driving circuit.
T3 Electronic
Interface
BNC
connectors
Fiberoptic
connectors
