DM200-01-0/1/2 CML
TM
Butterfly Transmitter Product Specification – May 2007
Finisar
I. Internal Optical Layout
Isolator
PD2
L1
L2
OSR
DFB
Fibre stub
Isolator
TEC
Beamsplitter
PD1
Window
Figure 1
Figure 1. CML internal layout
The DM200-01 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.
©
Finisar Corporation –10-May-07
Rev_A
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FINISAR [ FINISAR CORPORATION. ]
