
Block Diagram Of Transceiver
Transmitter Section
TRANSMITTER
RECEIVER
P
L
C
L
L
V
V
DATA+
DATA-
DATA+
PM
BIAS
TX-FAULT
I
2
P
TXd+
TXd-
TX-DIS
RXd+
RXd-
RXLOS
MOD_DEF(0)
MOD_DEF(2)
MOD_DEF(1)
DATA-
The
transmitter
section
consists of 1310nm FP
laser in an eye safe optical
subassembly (OSA) which
mates to the fiber cable.
The laser OSA is driven by
a LD driver IC which
converts differential input
LVPECL logic signals into
an analog laser driving
current.
TX-FAULT
TX Fault is an open collector/drain output, which should be pulled up with a 4.7K –
10K
resistor on the host board. Pull up voltage between 2.0V and VccT, R+0.3V. When
high, output indicates a laser fault of some kind. Low indicates normal operation. In the
low state, the output will be pulled to < 0.8V.
When sensing an improper power level in the laser driver, the SFP sets this signal
high and turns off the laser. TX-FAULT can be reset with the TX-DISABLE line. The
signal is in TTL level.
TX-DISABLE
TX disable is an input that is used to shut down the transmitter optical output. It is
pulled up within the module with a 4.7 – 10 K
resistor. Its states are: Low (0 – 0.8V):
Transmitter on; (>0.8, < 2.0V): Undefined; High (2.0 – 3.465V): Transmitter Disabled;
Open: Transmitter Disabled. The TX-DISABLE signal is high (TTL logic “1”) to turn off
the laser output. The laser will turn on when TX-DISABLE is low (TTL logic “0”).
TD-/+
These are the differential transmitter inputs. They are AC-coupled, differential lines
with 100
module and is thus not required on the host board. The inputs will accept differential
swings of 500 – 2400 mV (250 – 1200 mV single-ended), though it is recommended that
values between 500 and 1200 mV differential (250 – 600 mV single-ended) be used for
best EMI performance.
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