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Электронный компонент: HFCT-5218FM

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Agilent HFCT-5218M 622 Mb/s
Single Mode Laser Transceiver for
ATM, SONET OC-12/SDH STM-4 (L4.1)
Data Sheet
Description
The HFCT-5218 transceiver is a
high performance, cost effective
module for serial optical data
communications applications
specified for a signal rate of
622 MBd. It is designed to provide
a SONET/SDH compliant link for
622 Mb/s long reach links.
This module is designed for single
mode fiber and operates at a
nominal wavelength of 1300 nm.
It incorporates high performance,
reliable, long wavelength optical
devices and proven circuit
technology to give long life and
consistent service.
The transmitter section uses an
advanced Distributed Feedback
(DFB) laser with full IEC 825 and
CDRH Class 1 eye safety.
A pseudo-ECL logic interface
simplifies interface to external
circuitry.
Functional Description
Receiver Section
Design
The receiver section contains an
InGaAs/InP photodetector and a
preamplifier within the receptacle,
coupled to a postamp/decision
circuit on a separate circuit board.
The postamplifier is ac coupled to
the preamplifier as illustrated in
Figure 1. The coupling capacitor is
large enough to pass the SONET/
SDH test pattern at 622 Mbd
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 also shows a filter
network 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 also
reduce the sensitivity of the
receiver as the signal bit rate is
increased above 622 Mbd.
Features
SC duplex single mode
transceiver
Link distances up to 40 km with
9/125 m SMF
Fully Class 1 CDRH/IEC 825
compliant
Long reach SONET OC-12/ SDH
STM-4 (L4.1) compliant
Single +5 V power supply
operation and PECL logic
interfaces
Industry standard multisourced
1 x 9 mezzanine package style
Wave solder and aqueous wash
process compatible
Interchangeable with LED
multisourced 1 x 9 transceivers
Applications
SONET/SDH equipment
interconnect, STS-12/SDH
STM-4 Rate
Long reach (up to 40 km) ATM
links
2
Functional Description
Transmitter Section
Design
The transmitter section uses a
distributed feedback laser as its
optical source. The package of
this laser is designed to allow
repeatable coupling into single
mode fiber. In addition, this
package has been designed to be
compliant with IEC 825 eye safety
requirements under any single
fault condition. The optical output
is controlled by a custom IC
which detects the laser output via
the monitor photodiode, as shown
in Figure 2. This IC provides both
dc and ac current drive to the
laser to ensure correct
modulation, eye diagram and
extinction ratio over temperature,
supply voltage and life
Figure 1. Receiver Block Diagram
Figure 2. Simplified Transmitter Schematic
RECEIVER
RECEPTACLE
TRANS-
IMPEDANCE
PRE-
AMPLIFIER
FILTER
GND
LIMITING
AMPLIFIER
PECL
OUTPUT
BUFFER
PECL
OUTPUT
BUFFER
DATA OUT
SIGNAL
DETECT
CIRCUIT
SD
DATA OUT
DATA
DATA
PECL
INPUT
LASER
MODULATOR
LASER
LASER BIAS
DRIVER
LASER BIAS
CONTROL
PHOTODIODE
(rear facet monitor)
3
Applications Information
Recommended Circuit Schematic
When designing the HFCT-5218M
circuit interface, there are a few
fundamental guidelines to follow.
For example, in the Recommended
Circuit Schematic, Figure 3, the
differential PECL data lines
should be treated as 50 Ohm
Microstrip or stripline
transmission lines. This will help
to minimize the parasitic
inductance and capacitance
effects. Proper termination of the
differential data signal will
prevent reflections and ringing
which would compromise the
signal fidelity and generate
unwanted electrical noise. Locate
terminations at the received
signal end of the transmission
line. The terminations should be
the standard Thevenin-equivalent
50 ohm to V
CC
- 2 V termination.
Other standard PECL terminating
techniques may be used. The
length of these lines should be
kept short and of equal length to
prevent pulse-width distortion
from occurring. For the high-
speed signal lines, differential
signals should be used, not
single-ended signals. These
differential signals need to be
loaded symmetrically to prevent
unbalanced currents from flowing
which will cause distortion in the
signal.
The Signal Detect (SD) output of
the receiver is PECL logic and
must be loaded if it is to be used.
The signal detect circuit is much
slower that the data path, so the
ac noise generated by an
asymmetrical load is negligible.
Power consumption may be
reduced by using a higher than
normal load impedance for the SD
output. Transmission line effects
are not generally a problem as the
switching rate is slow.
Maintain a solid, low inductance
ground plane for returning signal
currents to the power supply.
Multilayer plane printed circuit
board is best for distribution of
V
CC
, returning ground currents,
forming transmission lines and
shielding. Also, it is important to
suppress noise from influencing
the fiber-optic transceiver
performance, especially the
receiver circuit. Proper power
Figure 3. Recommended Circuit Schematic for dc Coupling (at +5 V) between Optical
Transceiver and Physical Layer IC
MOUNTING POST
NO INTERNAL CONNECTION
HFCT-5218M
TOP VIEW
V
EER
RD
RD
SD
V
CCR
V
CCT
TD
TD
V
EET
1
2
3
4
5
6
7
8
9
C2
L1
L2
R2
R3
R1
R4
C5
C3
C4
R9
R10
V
CC
FILTER
AT V
CC
PINS
TRANSCEIVER
R5
R7
R6
R8
C6
RD
RD
SD
V
CC
TD
TD
TERMINATION
AT PHY
DEVICE
INPUTS
NOTES:
THE SPLIT-LOAD TERMINATIONS FOR PECL SIGNALS NEED TO BE LOCATED AT THE INPUT
OF DEVICES RECEIVING THOSE PECL SIGNALS. RECOMMEND MULTI-LAYER PRINTED
CIRCUIT BOARD WITH 50 OHM MICROSTRIP OR STRIPLINE SIGNAL PATHS BE USED.
R1 = R4 = R6 = R8 = R10 = 130 OHMS.
R2 = R3 = R5 = R7 = R9 = 82 OHMS.
C1 = C2 = C3 = C5 = C6 = 0.1 F.
C4 = C7 = 10 F.
L1 = L2 = 1 H COIL OR FERRITE INDUCTOR (see text comments).
TERMINATION
AT TRANSCEIVER
INPUTS
Rx
Rx
Tx
Tx
V
CC
V
CC
C1
C7
MOUNTING POST
NO INTERNAL CONNECTION
supply filtering of V
CC
for this
transceiver is accomplished by
using the recommended separate
filter circuits shown in Figure 3.
These filter circuits suppress V
CC
noise greater than 100 mV peak-
to-peak or less over a broad
frequency range. This prevents
receiver sensitivity degradation .
It is recommended that surface-
mount components be used. Use
tantalum capacitors for the 10 F
4
capacitors and monolithic,
ceramic bypass capacitors for the
0.1 F capacitors. Also, it is
recommended that a surface-
mount coil inductor of 1 H be
used. Ferrite beads can be used to
replace the coil inductors
when using quieter V
CC
supplies,
but a coil inductor is
recommended over a ferrite bead
to provide low frequency noise
filtering as well. Coils with a low,
series dc resistance (<0.7 ohms)
and high, self-resonating
frequency are recommended. All
power supply components need to
be placed physically next to the
V
CC
pins of the receiver and
transmitter. Use a good, uniform
ground plane with a minimum
number of holes to provide a low-
inductance ground current return
path for the signal and power
supply currents.
Although the front mounting posts
make contact with the metallized
housing these posts should not be
relied upon to provide adequate
electrical connection to the plated
housing. It is recommended to
either connect these front posts to
chassis ground or allow them to
remain unconnected. These front
posts should not be connected to
signal ground.
Figure 4 shows the recommended
board layout pattern.
In addition to these
recommendations, Agilent's
Application Engineering staff is
available for consulting on best
layout practices with various
vendors serializer/deserializer,
clock generator.
Reference Design
Agilent has developed a reference
design for multimode and single-
mode OC-12 ATM-SONET/SDH
applications shown in Figure 5.
This reference design uses a
Vitesse Semiconductor Inc.'s
VSC8117 clock recovery/clock
generation/serializer/deserializer
integrated circuit and a PMC-
Sierra Inc. PM5355 framer IC.
Application Note 1178 documents
the design, layout, testing and
performance of this reference
design. Gerber files, schematic
and application note are available
from the Agilent Fiber-Optics
Components' web site at the URL
of http://semiconductor.agilent.
com/fiber.
20.32
(0.800)
TOP VIEW
2 x 1.9 0.1
(0.075 0.004
20.32
(0.800)
2.54
(0.100)
9 x 0.8 0.1
(0.032 0.004
DIMENSIONS ARE IN MILLIMETERS (INCHES)
Figure 4. Recommended Board Layout Pattern
Figure 5. 622.08 Mb/s OC-12 ATM-SONET/SDH Reference Design Board
5
Electromagnetic Interference (EMI)
One of a circuit board designer's
foremost concerns is the control
of electromagnetic emissions
from electronic equipment.
Success in controlling generated
Electromagnetic Interference
(EMI) enables the designer to pass
a governmental agency's EMI
regulatory standard; and more
importantly, it reduces the
possibility of interference to
neighboring equipment. There are
three options available for the
HFCT-5218M with regard to EMI
shielding for providing the
designer with a means to achieve
good EMI performance. The EMI
performance of an enclosure
using these transceivers is
dependent on the chassis design.
Agilent encourages using standard
RF suppression practices and
avoiding poorly EMI-sealed
enclosures. In addition, Agilent
advises that for the best EMI
performance, the metalized case
must be connected to chassis
ground using one of the shield
options.
An un-shielded option, shown in
Figure 6 is available for the
HFCT-5218M fiber optic
transceiver. This unit is intended
for applications where EMI is
either not an issue for the
designer, or the unit resides in a
highly-shielded enclosure.
The first shielded option, option
EM, is for applications where the
position of the transceiver module
will extend outside the equipment
enclosure. The metallized plastic
package and integral external
metal shield of the transceiver
helps locally to terminate EM
fields to the chassis to prevent
their emissions outside the
enclosure. This metal shield
contacts the panel or enclosure on
the inside of the aperture on all
but the bottom side of the shield
and provides a good RF
connection to the panel. This
option can accommodate various
panel or enclosure thicknesses,
i.e. 1.02 mm (.04 in) min to
2.54 mm (0.1 in) max. The
reference plane for this panel
thickness variation is from the
front surface of the panel or
enclosure. The recommended
length for protruding the
HFCT-5218EM transceiver beyond
the front surface of the panel or
enclosure is 6.35 mm (0.25 in) .
With this option, there is flexibility
of positioning the module to fit
the specific need of the enclosure
design. (See Figure 7 for the
mechanical drawing dimensions
of this shield.)
The second shielded option,
option FM, is for applications that
are designed to have a flush
mounting of the module with
respect to the front of the panel or
enclosure. The flush-mount design
accommodates a large variety of
panel thickness, i.e. 1.02 mm
(.04 in) min to 2.54 mm (0.1 in)
max. Note the reference plane for
the flush-mount design is the
interior side of the panel or
enclosure. The recommended
distance from the centerline of the
transceiver front solder posts to
the inside wall of the panel is
13.82 mm (0.544 in) . This option
contacts the inside panel or
enclosure wall on all four sides of
this metal shield. (See Figure 8 for
the mechanical drawing
dimensions of this shield.)
Both shielded design options
connect only to the equipment
chassis and not to the signal or
logic ground of the circuit board
within the equipment closure. The
front panel aperture dimensions
are recommended in Figures 9 and
10. When layout of the printed
circuit board is done to
incorporate these metal-shielded
transceivers, keep the area on the
printed circuit board directly
under the external metal shield
free of any components and
circuit board traces. For
additional EMI performance
advantage, use duplex SC fiber-
optic connectors that have low
metal content inside the
connector. This lowers the ability
of the metal fiber-optic
connectors to couple EMI out
through the aperture of the panel
or enclosure.