4

Transmitter Section

Design

The transmitter section, Figure 3, uses a Multiple Quantum

Well 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 Class 1 and CDRH Class I eye safety

requirements. The optical output is controlled by a custom

IC which detects the laser output via the monitor photo-

diode. 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.

PCB mounting

The AFCT-5179xZ has two solderable mounting studs,

Figures 5 and 6. These studs are not electrically connected.

The transceiver is designed for common production

processes. It may be wave soldered and aqueous washed

providing the process plug is in place.

Each process plug can only be used once during process-

ing, although with subsequent use, it can be used as a

dust cover.

Figure 4. Recommended Circuit Schematic

DATA

DATA

PECL

INPUT

LASER

MODULATOR

LASER

LASER BIAS

DRIVER

LASER BIAS

CONTROL

PHOTODIODE

(rear facet monitor)

Figure 3. Simplified Transmitter Schematic

NO INTERNAL

CONNECTION

NO INTERNAL

CONNECTION

TOP VIEW

V

EER

1

RD

2

SD

4

V

CCR

5

V

CCT

6

TD

8

V

EET

9

NOTES:

THE SPLIT-LOAD TERMINATIONS FOR ECL SIGNALS NEED TO BE LOCATED AT

THE INPUT OF DEVICES RECEIVING THOSE ECL SIGNALS. RECOMMEND 4-LAYER

PRINTED CIRCUIT BOARD WITH 50

Ω MICROSTRIP SIGNAL PATHS BE USED.

R1 = R4 = R6 = R8 = R10 = 130

Ω

R2 = R3 = R5 = R7 = R9 = 82

Ω

C1 = C2 = 10 µF (see Figure 2)

C3 = C4 = C7 = C8 = 100 nF

C5 = C6 = 0.1 µF

L1 = L2 = 3.3 µH COIL OR FERRITE INDUCTOR.

TERMINATE

AT THE

DEVICE

INPUTS

VccFILTER

AT VccPINS

TRANSCEIVER

V

CC

C8

C1

L1 L2

TD

RD

3

TD

7

R8

RD

RD

V

CC

R5

R7

R6

C6

SD

R10

C7

C2

C3

C4

R4

V

CC

R2

R3

R1

TERMINATION

AT

TRANSCEIVER

INPUTS

TD

C5

R9