Isolated DFB Laser Module with PMF
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.
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
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.
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 µm, a cladding diameter of 123 µm—
128 µm, and a loose tube jacketed ﬁber 900 µm 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
§ ISO is a registered trademark of The International Organization for
(SILICON & ACRYLATE)
(ACRYLATE OR NYLON)
Figure 1. Polarization-Maintaining Fiber
Table 1. Pin Descriptions
3 Laser dc Bias (Cathode) (–)
4 Back-facet Monitor Anode (–)
5 Back-facet Monitor Cathode (+)
6 Thermoelectric Cooler (+)1
7 Thermoelectric Cooler (–)1
8 Case Ground
9 Case Ground
10 Case Ground
11 Laser Anode (+) 2
12 RF Laser Input Cathode (–)
13 Laser Anode (+) 2
14 Case Ground
1. A positive current through the thermoelectric heat pump cools the
2. Both leads should be grounded for optimum performance.
Figure 2. Circuit Schematic
Lucent Technologies Inc.