DM80-01-0/1/2 CML

F i n i s a r

©

Finisar Corporation –10-May-07

Rev_A

Page 2

I. Internal Optical Layout

Figure 1

The DM80-01 modules uses a 10Gb/s directly modulated DFB chip co-packaged with an

optical spectral re-shaper (OSR) element as shown in Figure 1. An optical isolator is

included between the DFB and the OSR while a beam-splitter component and 2

photodetectors are configured to allow frequency locking. Lens#1(L1) is used to

collimate the DFB laser output and pass the beam through the splitter and OSR, prior to

coupling into single-mode fiber using Lens#2 (L2). A second isolator is included in the

fiber pigtail to minimize the effect of external back-reflections on module performance.

II. Control Method

The schematic in Figure 2 shows the key components and control loops that are used to

operate the module. The output power of the DFB is monitored by photodetector PD1.

Photodetector PD2 monitors the back-reflection from the OSR. The photocurrent ratio

from the two detectors is used to lock the relative spectral locations of the laser and the

OSR via temperature control of the DFB using TEC#1. A second TEC (TEC#2) controls

the temperature of the OSR and locates the operating point of the OSR on the ITU grid

for DWDM applications.

TEC

DFB

PD2

PD1

OSR

L1

Isolator

Beamsplitter

L2

Fibre stub

Window

Isolator

TEC

DFB

TEC

DFB

PD2

PD2

PD1

PD1

OSR

OSR

L1

Isolator

Beamsplitter

L2

Fibre stub

Window

Isolator

Figure 1. CML internal layout