Oplink Communications, Inc.

RevA-PN.2009.06.25

18

19

3

TX DATA IN+

15

1µH coil or ferrite bead

(<0.2Ω series resistance)

0.1

TX DATA IN-

TX Disable

16

0.1

50Ω line

50Ω line

50Ω line

50Ω line

1, 9, 10, 11, 14, 17, 20

0.1

(100 to ground internally)

to 50Ω load

Vcc

3.3V

RX DATA OUT+

13

12

RX DATA OUT-

5

4

6

MOD_DEF(0)

MOD_DEF(1)

MOD_DEF(2)

LOS

to 50Ω load

8

R

RR

Vcc

3.3V

Example of SFP host board schematic

Figure 1 - Trade-off

curves in FDDI PMD

document

TRXNFEMM

Application Notes

Electrical Interface: Electrical interface: All signal interfaces are

compliant with the SFP MSA specification. The high speed DATA

interface is differential AC-coupled internally and can be directly

connected to a 3.3V SERDES IC. All low speed control and sense

output signals are open collector TTL compatible and should be

pulled up with a 4.7 - 10kΩ resistor on the host board.

Loss of Signal (LOS): The Loss of Signal circuit monitors the level

of the incoming optical signal and generates a logic HIGH when an

insufficient photocurrent is produced.

TX Fault: Per SFP MSA, pin 2 is TX Fault. This transceiver is LED based

and does not support TX Fault. Pin 2 is internally connected to

transmitter circuit ground (TX GND) to indicate normal operation.

TX Disable:When theTX Disable pin is at logic HIGH, the transmitter

optical output is disabled (less than -45dBm).

Serial Identification: The module definition of SFP is indicated by

the three module definition pins, MOD_DEF(0), MOD_DEF(1) and

MOD_DEF(2). Upon power up, MOD_DEF(1:2) appear as NC (no

connection), and MOD_DEF(0) is TTL LOW. When the host system

detects this condition, it activates the serial protocol (standard two-

The negative edge clocks data from the SFP EEPROM.

The serial data signal (SDA) is for serial data transfer. The host uses

SDA in conjunction with SCL to mark the start and end of serial

protocol activation.

The data transfer protocol and the details of the mandatory and

vendor specific data structures are defined in the SFP MSA.

Power Supply and Grounding: The power supply line should be

well-filtered. All 0.1μF power supply bypass capacitors should be as

close to the transceiver module as possible.

4

TRXNFEMM

R: 4.7 to 10kΩ

100

120

140

160

180

200

1280

1300

1320

1340

1360

1380

SOURCE CENTER WAVELENGTH (nm)

1.5

2.0

2.5

3.0

3.5

3.0

3.5

Source rise & fall time (ns)