Wavelength-Selected D2525P
Isolated DFB Laser Module with PMF
Data Sheet
March 2000
Description
(continued)
Controlled Feedback
The module contains an internal optical isolator that sup-
presses optical feedback in laser-based, fiber-optic sys-
tems. Light reflected back to the laser is attenuated a
minimum of 30 dB.
CORE
STRESS ROD
PRINCIPAL POLARIZATION
AXIS
CLADDING
INNER COATING
(SILICON & ACRYLATE)
OUTER COATING
(ACRYLATE OR NYLON)
1-771(C).a
Controlled Temperature
An integral thermoelectric cooler (TEC) provides stable
thermal characteristics. The TEC allows for heating and
cooling of the laser chip to maintain a temperature of 25
°
C
for case temperatures from –40
°
C to +70
°
C. The laser
temperature is monitored by the internal thermistor, which
can be used with external circuitry to control the laser chip
temperature.
Figure 1. Polarization-Maintaining Fiber
Pin Information
Table 1. Pin Descriptions
Pin
Name
Thermistor
Thermistor
Laser dc Bias (Cathode) (–)
Back-facet Monitor Anode (–)
Back-facet Monitor Cathode (+)
Thermoelectric Cooler (+)
1
Thermoelectric Cooler (–)
1
Case Ground
Case Ground
Case Ground
Laser Anode (+)
2
RF Laser Input Cathode (–)
Laser Anode (+)
2
Case Ground
Controlled Power
An internal, InGaAs, PIN photodiode functions as the back-
facet monitor. The photodiode monitors emission from the
rear facet of the laser and, when used in conjunction with
control circuitry, can control optical power launched into the
fiber. Normally, this configuration is used in a feedback
arrangement to maintain consistent laser output power.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Standard Package
The laser module is fabricated in a 14-pin, hermetic, metal/
ceramic butterfly package that incorporates a bias tee that
separates the dc-bias path from the RF input. The RF input
has a nominal 25
Ω
impedance.
The laser module is equipped with
Fujikura*
polarization-
maintaining fiber (PMF). The fiber is PANDA type and is the
same fiber that is used on Lucent Technologies Microelec-
tronics Group’s lithium niobate modulators. It has a mode
field diameter of 10.5
µ
m, a cladding diameter of 123
µ
m—
128
µ
m, and a loose tube jacketed fiber 900
µ
m in diame-
ter. The pigtail is terminated with an
ST
®
ferrule
†
. Figure 1
shows the orientation of polarization in the fiber.
Lucent’s optoelectronic components are being qualified to
rigorous internal standards that are consistent with
Telcor-
dia Technologies
‡
TR-NWT-000468. All design and manu-
facturing operations are
ISO
§
9001 certified. The module is
being fully qualified for central office applications.
*
Fujikura
is a registered trademark of Fujikura Ltd.
† The
ST
ferrule key is not aligned to slow axis of fiber. Connector is
intended for testing purposes only.
‡
Telcordia Technologies
is a trademark of Bell Communications
Research, Inc.
§
ISO
is a registered trademark of The International Organization for
Standardization.
1. A positive current through the thermoelectric heat pump cools the
laser.
2. Both leads should be grounded for optimum performance.
7
–
6
+
5
+
4
–
L1
160 nH
TEC
3
–
TH
10 kΩ
2
1
PACKAGE
GROUNDS
+
8
9
10
11
R1
20
Ω
–
12
ISOLATOR
+
13
14
1-567
Top view.
Figure 2. Circuit Schematic
Lucent Technologies Inc.
2
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