AFCT-5941xTxZ
Single Mode SFF Transceivers for SONET OC-48/SDH STM-16 Multirate
Operation (Part
of the Avago Technologies’ METRAK family)
Data Sheet
Description
The AFCT-5941xTxZ are high performance, cost effective
modules for serial optical data communications applica-
tions. They are designed to provide SONET/SDH compli-
ant links at 2488 Mb/s for intermediate reach links.
The modules are designed for single mode fiber and
operate at a nominal wavelength of 1300 nm. They in-
corporate high performance, reliable, long wavelength
optical devices and proven circuit technology to give
long life and consistent service.
The transmitter in the AFCT-5941TLZ/ATLZ/TGZ/ATGZ
uses a Distributed Feedback (DFB) Laser. The transmitter
has full IEC 825 and CDRH Class 1 eye safety.
For each device the receiver section uses an MOVPE
grown planar SEDET PIN photodetector for low dark
current and excellent responsivity.
A positive ECL logic interface simplifies interface to ex-
ternal circuitry.
The transceivers are supplied in the new industry stan-
dard 2 x 5 DIP style package with the LC fiber connector
interface and is footprint compatible with SFF Multi
Source Agreement (MSA).
Features
•
AFCT-5941TLZ/ATLZ: Links of 15 km with 9/125 µm
single mode fiber (SMF)
•
Multisourced 2 x 5 package style with LC receptacle
•
Single +3.3 V power supply
•
Temperaturerange:
•
•
•
•
•
AFCT-5941TLZ/TGZ: 0°C to +70°C
AFCT-5941ATLZ/ATGZ: -20°C to +85°C
Wave solder and aqueous wash process compatible
Manufactured in an ISO9002 certified facility
RoHS compliant
Fully Class 1 CDRH/IEC 825 compliant
Compliant with ITU-T G.957, STM-16, I-16 and S-16.1
Optical Interfaces
•
AFCT-5941TLZ/ATLZ: with EMI nose shield
•
AFCT-5941TGZ/ATGZ: no EMI nose shield
•
Receiver output squelch function enabled
Applications
•
SONET/SDH equipment interconnect
•
Client Interface on Metro Gateways and Edge Switch-
es
Functional Description
Receiver Section
Design
The receiver section for the AFCT-5941xTxZ contains an
InGaAs/InP photo detector and a preamplifier mount-
ed 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 perfor-
mance penalty. For codes which have a significantly
lower frequency content, jitter and pulse distortion
could be degraded.
The receiver outputs are squelched at Signal Detect
deasserts. That is, when the light input decreases to
typical -27 dBm or less, the Signal Detect deasserts i.e.
the SD Output goes to a PECL low state. This forces the
DATA OUT and DATA OUT Bar to go PECL levels high
and low respectively.
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 re-
ceiver as the signal bit rate is increased above 2.7 Gb/s.
Noise Immunity
The receiver includes internal circuit components to
filter power supply noise. However under some condi-
tions of EMI and power supply noise, external power
supply filtering may be necessary (see Application Sec-
tion).
The Signal Detect Circuit
The signal detect circuit works by sensing the peak level
of the received signal and comparing this level to a ref-
erence. The SD output is low voltage TTL.
TRANS-
IMPEDANCE
PRE-
AMPLIFIER
FILTER
AMPLIFIER
DATA OUT
PECL
OUTPUT
BUFFER
DATA OUT
GND
SIGNAL
DETECT
CIRCUIT
TTL
OUTPUT
BUFFER
SD
Figure 1. Receiver Block Diagram
2
Functional Description
Transmitter Section
Design
A schematic diagram for the transmitter is shown in
Figure 2. AFCT-5941TLZ/TGZ/ATLZ/ATGZ uses a DFB la-
ser as its laser source. The transmitter optical packages
has been designed to be compliant with IEC 825 eye
safety requirements under any single fault condition
and CDRH under normal operating conditions. The
optical output is controlled by a custom IC that detects
the laser output via the monitor photodiode. 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 operating
life.
PHOTODIODE
(rear facet monitor)
DFB
LASER
DATA
DATA
PECL
INPUT
LASER
MODULATOR
LASER
BIAS
DRIVER
LASER
BIAS
CONTROL
Figure 2. Simplified Transmitter Schematic
3
Package
The overall package concept for the device consists
of the following basic elements; two optical subas-
semblies, a electrical subassembly and the housing as
illustrated in the block diagram in Figure 3.
The package outline drawing and pin out are shown in
Figures 4 and 5. The details of this package outline and
pin out are compliant with the multisource definition
of the 2 x 5 DIP.
A metallic nose clip provides connection to chassis
ground for both EMI and thermal dissipation.
The electrical subassembly consists of high volume
multilayer printed circuit boards on which the IC and
various surface-mounted passive circuit elements are
attached.
The receiver electrical subassembly includes an inter-
R
X
SUPPLY
nal shield for the electrical and optical subassembly to
ensure high immunity to external EMI fields.
The optical subassemblies are attached to the electrical
subassembly. These two units are then fitted within the
outer housing of the transceiver. The housing is then
encased with a metal EMI protective shield.
The electrical subassembly carries the signal pins that
exit from the bottom of the transceiver. The solder
posts are designed to provide the mechanical strength
required to withstand the loads imposed on the trans-
ceiver by mating with the LC connectored fiber cables.
Although they are not connected electrically to the
transceiver, it is recommended to connect them to
chassis ground.
*
DATA OUT
DATA OUT
SIGNAL
DETECT
DATA IN
DATA IN
Tx DISABLE
QUANTIZER IC
R
X
GROUND
T
X
GROUND
LASER BIAS
MONITORING
LASER DRIVER
AND CONTROL
CIRCUIT
LASER DIODE
OUTPUT POWER
MONITORING
PIN PHOTODIODE
PREAMPLIFIER
SUBASSEMBLY
LC
RECEPTACLE
LASER
OPTICAL
SUBASSEMBLY
T
X
SUPPLY
CASE
* NOSE CLIP PROVIDES CONNECTION TO CHASSIS GROUND FOR BOTH EMI AND THERMAL DISSIPATION.
Figure 3. Block Diagram
4
Figure 4. AFCT-5941xTxZ Package Outline Drawing
5
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