afbr-820bz Avago Technologies, afbr-820bz Datasheet - Page 2

• Manufacturer Part Number: afbr-820bz
• Description: Twelve-channel Transmitter And Receiver Pluggable, Parallel-fiber-optic Modules
• Manufacturer: Avago Technologies

Transmitter Module
The optical transmitter module (see Figure 1) incorporates
a 12-channel VCSEL (Vertical Cavity Surface Emitting Laser)
array, a 12-channel input buffer and laser driver, diagnos-
tic monitors, control and bias blocks. The transmitter is
designed for IEC-60825 and CDRH eye safety compliance;
Class 1M out of the module. The Tx Input Buffer provides
CML compatible differential inputs (presenting a nominal
differential input impedance of 100 Ohms and a nominal
common mode impedance to signal ground of 25 Ohms)
for the high speed electrical interface that can operate
over a wide common mode range without requiring DC
blocking capacitors. For module control and interroga-
tion, the control interface (LVTTL compatible) incorpo-
rates a Two Wire Serial (TWS) interface of clock and data
signals and dedicated signals for host interrupt, module
address setting and module reset. Diagnostic monitors for
VCSEL bias, light output (LOP), temperature, both supply
voltages and elapsed operating time are implemented
and results are available through the TWS interface.
Over the TWS interface, the user can, for individual
channels, control (flip) polarity of the differential inputs,
de-activate channels, place channels into margin mode,
Figure 1. Transmitter Block Diagram
2
Din[11:0][p/n] (24)
Adr[2:0] (3)
Vcc33 (4)
Vcc25 (2)
Gnd
ResetL
SCL
SDA
IntL
Tx Input Buffer
12 Channels
Control
Bias
Diagnostic Monitors
Laser Driver
12 Channels
disable the squelch function and program input equaliza-
tion levels to reduce the effect of long PCB traces. A reset
for the control registers is available. Serial ID information
and alarm thresholds are provided. To reduce the need for
polling, the TWS interface is augmented with an interrupt
signal for the host.
Alarm thresholds are established for the monitored
attributes. Flags are set and interrupts generated when
the attributes are outside the thresholds. Flags are also set
and interrupts generated for loss of input signal (LOS) and
transmitter fault conditions. All flags are latched and will
remain set even if the condition initiating the latch clears
and operation resumes. All interrupts can be masked and
flags are reset by reading the appropriate flag register. The
optical output will squelch for loss of input signal unless
squelch is disabled. Fault detection or channel deactiva-
tion through the TWS interface will disable the channel.
Status, alarm and fault information are available via the
TWS interface. The interrupt signal (selectable via the TWS
interface as a pulse or static level) is provided to inform
hosts of an assertion of an alarm, LOS and/or Tx fault.