HFCT-5942 HP [Agilent(Hewlett-Packard)], HFCT-5942 Datasheet - Page 2

• Manufacturer Part Number: HFCT-5942
• Description: Single Mode Laser Small Form Factor Transceivers for ATM, SONET OC-48/SDH STM-16 Part of the Agilent METRAK family
• Manufacturer: HP [Agilent(Hewlett-Packard)]

Functional Description
Receiver Section
Design
The receiver section for the
HFCT-5942xxx 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 27
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 2488 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.
Figure 1. Receiver Block Diagram
2
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 2488 Mb/s.
As an optional feature the
device also incorporates a
photodetector bias circuit. The
circuit works by providing a
mirrored output of the bias
current within the photodiode.
This output must be connected
to V
by connecting through a series
resistor (see Application
Section).
CC
AMPLIFIER
and can be monitored
CIRCUIT
SIGNAL
DETECT
PECL
OUTPUT
BUFFER
TTL
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 peak level of
the received signal and
comparing this level to a
reference. The SD output is
low voltage TTL.
DATA OUT
DATA OUT
SD