HFCT-5964ATG NEL [Nel Frequency Controls,inc], HFCT-5964ATG Datasheet - Page 2

• Manufacturer Part Number: HFCT-5964ATG
• Description: ATG Single Mode Laser Small Form Factor Transceivers for ATM, SONET OC-3 /SDH STM-1 Part of the Agilent METRAK family
• Manufacturer: NEL [Nel Frequency Controls,inc]

Functional Description
Receiver Section
Design
The receiver section for the
HFCT-5964TL/TG/NL/NG/ATL/
ATG contains an InGaAs/InP
photo detector and a
preamplifier mounted in an
optical subassembly. This optical
subassembly is coupled to a
postamp/decision circuit on a
circuit board. The design of the
optical assembly is such that it
provides better than 14 dB
Optical Return Loss (ORL).
The postamplifier is ac coupled
to the preamplifier as illustrated
in Figure 1. The coupling
capacitors are large enough to
pass the SONET/SDH test
pattern at 155 Mb/s without
significant distortion or
performance penalty. If a lower
signal rate, or a code which has
significantly more low frequency
content is used, sensitivity, jitter
and pulse distortion could be
degraded.
2
Figure 1. Receiver Block Diagram
PHOTODETECTOR
BIAS
TRANS-
IMPEDANCE
PRE-
AMPLIFIER
GND
FILTER
Figure 1 also shows a filter
function which limits the
bandwidth of the preamp output
signal. The filter is designed to
bandlimit the preamp output
noise and thus improve the
receiver sensitivity.
These components will reduce
the sensitivity of the receiver as
the signal bit rate is increased
above 155 Mb/s.
The device incorporates a
photodetector bias circuit. This
output must be connected to V
and can be monitored by
connecting through a series
resistor (see Application
Section).
AMPLIFIER
CIRCUIT
SIGNAL
DETECT
CC
LVPECL
OUTPUT
BUFFER
LVTTL
OUTPUT
BUFFER
Noise Immunity
The receiver includes internal
circuit components to filter
power supply noise. However
under some conditions of EMI
and power supply noise,
external power supply filtering
may be necessary (see
Application Section).
The Signal Detect Circuit
The signal detect circuit works
by sensing the level of the
received signal and comparing
this level to a reference. The SD
output is +3.3 V TTL.
DATA OUT
DATA OUT
SD